Checkmate is a strategic term used in the game of chess to indicate the King’s being irredeemably cornered, attacked, and finished by any opponent of the King.
It can also be used as a metaphor to refer to anyone who is attacked and having no means of escape. In the case of Howard Lumumba’s play, ‘Checkmate’, the one getting checkmated is Kingston (Jarad Itaro) although we don’t know it until the end of the play.