IPA: /ˈfʊl.bæk/
KK: /ˈfʊlˌbæk/
A player in football or other sports who plays behind the quarterback or near the defensive goal, mainly responsible for blocking and sometimes carrying the ball.
The fullback made a crucial block to help the running back score a touchdown.
Fullback → It is formed from "full" (from Old English "full", meaning complete or filled) and "back" (from Old English "bæc", meaning the rear part of something). The word "fullback" refers to a player in football who is positioned at the back and is responsible for both defense and offense, thus being a complete player in that position.
Think of someone who is 'complete' ('full') at the 'back' of the team, ready to support both defense and offense.