n. (American football) the position of a player on a football team who is stationed behind the line of scrimmage

n. a fighter who holds out against attack

n. someone who expounds and interprets or explains

n. a person who argues to defend or justify some policy or institution; "an apologist for capital punishment"

n. (football) a person who plays in the backfield

n. a person who keeps watch over something or someone

n. the codefendant (especially in a divorce proceeding) who is accused of adultery with the corespondent