An enlisted person in the U.S. Army or Marine Corps of the lowest rank.
The Air Force and Navy have different ranks.
Lawrence: Hey! I just joined the Marine Corps!
Joanne: Cool! I just joined the U.S. Army after completing ROTC.
Jason: Haha, you guys are Privates. =]
A Noncommissioned Officer (NCO) in various armed forces, of a rank immediately below sergeant, or, in Canada, a master corporal. Also the rank above a Private.
Lawrence: Hey I just got promoted from a Private!
Jason: Oh! Now you're a Corporal!