(verb) It means to relax. You say it to people to de-stress and unwind. It can be used interchangeably with "take a chill pill" or "take a load off" Or if a conversation is too heated and it needs to be cooled down, people will say "A/C!"
steve: WOAH! STFU! YOU'RE STUPID AND ARROGANT!
ben: NO, YOU'RE SUCH A BITCH FOR EVEN CARING!
mark: you guys, A/C. A/C.
A group of 10 to 15 year old boys on Honda-Tech that aspire to own pink and orange Japanese economy cars and 48" chrome "spinna" rims. Additionally, there are also a disproportionately large group of 20-somethings that feel painting and applying decals and wings to a used Japanese car is quite possibly the best way to pick up a new "baby momma" after the old one has sold her body for crack.
Yo dawg! You see that fresh Civic in A/C? It had a mad tyte fishtank in it! R0TA 4 LYFE!
And dying in yo' bed many years from now, would ya be willing ta trade all da days from dis here day ta dat fo' one chance, just one chance, ta come back here as young men an' tell our enemies dat dey may take our lives but dey will never take our freedom ... YUB NUB!