A misread is a move or line of play that is predicated on a mistake in reading. Typical sorts of misreads include not spotting the opponent's best reply, forgetting that some stones are in atari ("atari blindness"), failing to see a ladder or ladder-breaker ("misreading the ladder"), and ignoring nearby stones.
A particularly damaging or imbecilic misread may be a blunder. However, not all mistakes are misreads. See zokusuji, overplay, thin, and overconcentrated for examples of mistakes that are not necessarily misreads.