an unexpected hit that movie was the sleeper of the summer tropical fish that resembles a goby and rests quietly on the bottom in shallow water a piece of furniture that can be opened up into a bed pajamas with feet; worn by children a passenger car that has berths for sleeping one of the cross braces that support the rails on a railway track the British call a railroad tie a sleeper a rester who is sleeping an unexpected achiever of success the winner was a true sleeper — no one expected him to get it a spy or saboteur or terrorist planted in an enemy country who lives there as a law-abiding citizen until activated by a prearranged signal