This list includes 36 Slang words that start with O, from “OD” to “ozzie”. They are informal and often regional, ranging from playful nicknames to blunt insults, useful for writers and learners.

Slang words that start with O are informal terms beginning with the letter O used in casual speech and online chat. Many come from subcultures or shortened phrases, with several entering wider use through music and social media.

Below you’ll find the table with Word, Meaning, Region, Register, Example, and Source.

Word: The listed slang term itself, shown exactly as it appears in speech or writing so you can recognize it quickly.

Meaning: A concise definition that explains common use and nuance so you can grasp the intended sense in context.

Region: Shows where the term is commonly used, helping you judge whether it’s local, national, or international.

Register: Indicates formality and tone, so you know if a term is casual, offensive, playful, or slangy in everyday speech.

Example: A short sentence showing the term in natural use, giving you a quick model for writing or conversation.

Source: Notes where the term appears or its earliest known use, helping you assess recency and cultural origin.

Slang words that start with O

Word Part of Speech Meaning Region/Register Description
OG noun/adjective original gangster; respected veteran US, informal Hip-hop-origin term for founders or veterans; used broadly as praise. “She’s an OG in the scene.”
obvs adverb obviously US/UK, internet informal Abbreviated, casual form of “obviously”; common in texting and social posts. “Obvs you’re coming, right?”
oik noun unpleasant or uncouth person UK, pejorative/informal British insult for someone rude or low-class; dated but still used. “Don’t be such an oik.”
ole adjective/interjection informal form of “old” or exclamation US, informal/dialect Colloquial spelling (e.g., “good ole days”); common in regional speech. “Good ole Joe fixed it.”
oldie noun something, usually a song, from long ago US/UK, informal Casual term for an old song or classic item. “That oldie still gets radio play.”
oddball noun/adjective eccentric or strange person/thing US/UK, informal Common informal label for someone quirky. “He’s a lovable oddball.”
off verb/adjective to kill; not right or broken US, informal/slang “To off” is slang for kill; “off” also meaning bad/not right. “They offed the witness.”
offie noun off-licence shop; place selling alcohol UK, informal British colloquial for a liquor store. “Grab beer from the offie.”
offsider noun assistant or sidekick AUS, informal Australian slang for a helper or teammate. “Her offsider carried the gear.”
oxy noun oxycodone (prescription opioid) US, drug slang Street shorthand for the opioid oxycodone; used in drug contexts. “He was buying oxy on the street.”
oz noun ounce; also Australia (slang) US/UK/AUS, informal Common abbreviation for ounce (weed/silver) and informal name for Australia (“Oz”). “He bought an oz of bud.”
ozzie noun Australian person (informal demonym) AUS/UK/US, informal Casual/diminutive term for an Australian. “We’re meeting some Ozzies abroad.”
oreo noun pejorative for person seen as betraying racial identity US, pejorative/slur Racial slur for someone perceived as “acting white”; offensive. “He was called an ‘Oreo’—that’s hurtful.”
oop interjection/verb expression after a mistake or surprise US/internet, informal Internet meme/interjection popularized by videos; used when one slips up. “Oop—I dropped it.”
oof interjection expression of pain, shock, or embarrassment Internet/US, informal Internet/gaming exclamation for physical or emotional impact. “Oof—that game hurt my rank.”
omg interjection “oh my God” (surprise, emphasis) Global, internet informal Widely used initialism in texts/social media for surprise. “OMG that concert was wild!”
orly interjection “oh, really?” (skeptical/surprised) Internet/US/UK, informal Sarcastic or genuine questioning reply online. “Orly? Prove it.”
op noun/verb opponent; original poster (internet) US/internet/rap, informal Short for “opponent” in street slang and “original poster” online. “Don’t trust the op in that thread.”
oppo noun opponent or opposing player UK/AUS, informal British/Australian slang for an adversary or rival. “Watch your back—your oppo is close.”
opp noun opponent or enemy (rap/urban slang) US, urban slang Common in rap/gang contexts meaning enemy or rival. “They beefed with their opps.”
own verb to dominate, defeat, embarrass US/internet, informal Slang for decisively beating someone or proving superiority. “She owned him in the debate.”
outta preposition/phrase contraction of “out of” US/UK, informal Casual spoken/spelled contraction in speech and text. “I’m outta here.”
outie noun/interjection protruding bellybutton; I’m leaving US/UK, informal Literal for navel shape; slangy short for “I’m out (leaving)”. “I’m an outie.” / “Outie!”
owt pronoun anything (Northern English dialect) UK, regional/dialectal Northern English/Scouse dialectal word meaning “anything”; informal. “Is there owt I can do?”
oy interjection attention-getting exclamation (“hey”) UK/Yiddish, informal Used to call attention or express annoyance. “Oy! Watch it!”
OTT adjective over the top, excessive UK/AUS/US, informal Abbreviation used in casual speech to criticize excessiveness. “Her outfit was OTT.”
omerta noun code of silence, especially about crime US/UK, informal/loanword Italian loanword used in English slang about mafia-like silence. “Nobody spoke—omertà won.”
one-up verb to outdo or gain advantage over someone US/UK, informal Common slang for trying to top another person’s story or deed. “He always one-ups my achievements.”
one-off adjective single, unique occurrence US/UK, informal Casual descriptor for something done once or not repeatable. “It was a one-off performance.”
oner noun single continuous take in film or stunt US/UK, industry slang Filmmaking slang for a continuous-shot scene; used in production talk. “We need a smooth oner for that scene.”
OD verb/noun to overdose; an overdose US, informal/slang Common slang/initialism for overdosing or overdose incident. “He almost OD’d last year.”
old-school adjective reminiscent of an earlier style or method US/UK, informal Hyphenated colloquial term praising vintage or classic style. “That’s so old-school cool.”
oopsy interjection mild exclamation for a small mistake US/UK, informal Playful form of “oops,” often jokingly apologetic. “Oopsy—I spilled my drink.”
okay interjection/adjective all right; acceptable (informal) Global, informal Widely used informal term expressing assent or mediocrity. “Okay, let’s go.”
ocker noun stereotypically uncultured Australian man AUS, informal/pejorative Australian slang for a rough, boisterous male stereotype. “He’s a bit of an ocker.”
otter noun gay slang: a lean/hairy man US/UK, LGBT slang/informal Community slang for a smaller, hairy gay man; playful descriptor. “He’s more of an otter than a bear.”

Descriptions

OG
obvs
oik
ole
oldie
oddball
off
offie
offsider
oxy
oz
ozzie
oreo
oop
oof
omg
orly
op
oppo
opp
own
outta
outie
owt
oy
OTT
omerta
one-up
one-off
oner
OD
old-school
oopsy
okay
ocker
otter
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