AR

Abbreviation.

1(countable, weaponry) An AR-15 personal semi-automatic rifle, M-16 assault rifle, M-4 carbine, derivative or related gun; the Armalite AR family and derivatives.
2(countable, weaponry, informal) An assault rifle or automatic rifle.
3(uncountable or plural only, accounting) Initialism of accounts receivable.
4(philately, postal) Initialism of acknowledgment of receipt.
5(age regression, paraphilia) Initialism of age regression.
6(uncountable, computing) Initialism of augmented reality.
7(fandom slang) Initialism of alternate reality.
8(countable, sports, US) Initialism of American record, national record for the United States.