also full-back, 1882 in sports, from full (adj.) + back (n.).

(n) (football) the running back who plays the fullback position on the offensive team(n) (American football) the position of a back on a football team(v) play the fullback

They are the player wearing jersey number 15. They act as the last line of defense against running attacks by the opposing three-quarter backs. The full back is expected to field high kicks from the o [..]

 

The running back closer to the offensive line when there are multiple running backs in a formation. Usually used as a blocker for the tailback, but can also carry the ball and catch passes.

A defensive player, playing closest to one's own goal.  

A large running back who lines up behind the quarterback. Much heavier and stronger than ball-carrying running backs known as halfbacks, the fullback often acts as an extra blocker and usually only carries the ball in situations where a small amount of yards are needed to gain a first down and a strong running style is the best approach.

(American football) An offensive back whose primary jobs are to block in advance of the halfback on running plays and for the quarterback on passing plays. (field hockey)