muggins

1a :  a provision in many games played in England that if a player fails to record an earned score promptly his opponent may say muggins and claim that score —used especially in cribbage and dominoes b :  a dominoes game identical with sniff except that the muggins provision is included c :  any of various card games in which a score overlooked may be claimed by saying muggins or in which the player with the worst score is called muggins —used especially in children's games

2 :  simpleton had seen too many muggins come bowing and smiling — Enid Bagnold