Initialism of object-oriented ontology.
"The conference featured several papers on OOO, exploring how objects exist independently of human perception."
"The mysterious sound she heard was just her cat making ooo noises while sleeping."
Initialism of out of office.
"The email signature at the bottom indicates that he is ooo until next Tuesday."
In plain English: Ooo is slang for something that looks really good and makes you want to buy it.
"The ooo texture of the fabric felt surprisingly smooth against my skin."
An abbreviation for hugs, usually placed at the end of a letter or in text messaging; often placed alongside xxx.
"Please check my email signature which states I am ooo from next Monday until Friday."
An abbreviation for Out of Office, a phrase often used in professional contexts to indicate that someone is unavailable for work (usually because they are on vacation).