private first class

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A noncommissioned rank in the U.S. Army that is above private and below corporal or in the U.S. Marine Corps that is above private and below lance corporal.
2. n. One who holds this rank.

Wiktionary

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