A slang term in football that refers to the strong-side linebacker, a defensive player position that lines up against the strong side of the offensive line.
"Sam" is used as a shorthand term in order to easily communicate the need for a defensive blitz and/or to distinguish a player's position quickly. In addition to Sam, there are two other colloquial terms for linebacker positions: "Mike" and "Will", indicating the middle and weak-side linebackers, specifically.
Sams are a typical staple of the 4-3 defense. The strong-side linebacker lines up on the strong side of the offensive line, most often paired against a tight end. The most desirable qualities in a strong-side linebacker are strength and quickness. One of the responsibilities of the strong-side linebacker is to stop the run, as a running back will often trail behind a blocking tight end. The Sam also acts to defend the short pass-the position's proximity to a tight end makes this matchup possible.