Home : Online Slang : AM ALT | AMAZN Tweet AM Meaning Antemeridian Type Abbreviation Rank ★ ★ ★  Common Usage General (not just online) Comments AM means antemeridian. It is an abbreviation that refers to the hours between midnight and noon, i.e. 8:30 AM in the morning. Updated June 28, 2016 All "A" Slang Terms Online Slang Home Print