A Linebacker is commonly referred to as an LB.
Yes, it is a football term
Linebacker
A linebacker (LB or backer) is a playing position in American football and Canadian football. Linebackers are members of the defensive team, and line up approximately three to five yards (4 m) behind the line of scrimmage, behind the defensive linemen, and therefore "back up the line". Linebackers generally align themselves before the ball is snapped by standing upright in a "two-point stance" (as opposed to the defensive linemen, who put one or two hands on the ground for a "
and probably should be referred to simply as "tackle"—or "defensive tackle" (DT) in a player roster (see below).
The linebacker (LB) positions are straightforwardly distinguished as inside (ILB) and outside (OLB). When there are only three linebackers, the one inside is labeled middle linebacker (MLB), and the outside positions can instead be named as left and right.
The defense's halfbacks have been renamed cornerbacks (CB), a fitting term given that they play at the