* A misspelling: Perhaps it's meant to be another acronym or word.
* A specific inside joke: It could be a term used by a particular group of friends or community.
* A new, emerging acronym: It's possible it's a recently created acronym that hasn't yet gained widespread use.
To figure out what OMAO means in your context, you'd need more information:
* Where did you see it? (e.g., in a text message, on social media, in a forum)
* What was the context? (e.g., what was the conversation about?)
* Who said it? (e.g., a friend, a stranger, someone online)
Knowing these details could help you decipher the meaning of "OMAO."