The offensive football players who line up behind the linemen WordNet 3.0 & Open English WordNet

The offensive backfield is an ambiguous generic term of football, which includes: a place, namely the area of an American football field behind the line of scrimmage; and a group classification of certain players positioned there, i.e., members of offense who begin plays behind the line, typically including any backs on the field, such as the quarterback, halfbacks and fullback. Wikipedia

Area and players behind the line of scrimmage in American/Canadian football Wikidata

The area of play behind either the offensive or defensive line. Wiktionary