Emily Dickinson Lexicon

GAM'MON, v.t.²

1. In the game of back-gammon, the party that, by fortunate throws of the dice or by superior skill in moving, withdraws all his men from the board, before his antagonist has been able to get his men home and withdraw any of them from his table, gammons his antagonist.
2. To impose on a person by making him believe improbable stories. Pickwick Papers.