the occurrence of incoming water (between a low tide and the following high tide); "a tide in the affairs of men which, taken at the flood, leads on to fortune" -Shakespeare
a chess move constituting an inescapable and indefensible attack on the opponent's king
complete victory
place an opponent's king under an attack from which it cannot escape and thus ending the game; "Kasparov checkmated his opponent after only a few moves"