private first class

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A noncommissioned rank in the US Army that is above private and below corporal or in the US Marine Corps that is above private and below lance corporal.
• noun One who holds this rank.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun US An enlisted rank in the United States Army, of rank E-3, ranking above a private and below a corporal or specialist.
• noun US An enlisted rank in the United States Marine Corps, of rank E-2, ranking above a private and below a lance corporal.