Backfield (noun)

1. In American football, the area behind the line of scrimmage and the position of the players in that area, including the halfback and fullback.
2. The area behind the main line of attack or defense, especially in sports.

Origin:

Derived from the phrase 'back field' meaning 'field behind the line of scrimmage'.

Examples:

1. The quarterback handed off the ball to the running back in the backfield.
2. The quarterback looked to his right, scanning the backfield for an open receiver.
3. The fullback ran through the gap in the line, picking up big yards in the backfield.
4. The defense was caught off guard by the halfback's sudden burst through the backfield.
5. The coach called a trick play, with the wide receiver taking the handoff in the backfield and running for a touchdown.