Swarm1  —n. 1 cluster of bees leaving the hive with the queen to establish a new colony. 2 large cluster of insects, birds, or people. 3 (in pl.; foll. By of) great numbers. —v. 1 move in or form a swarm. 2 (foll. By with) (of a place) be overrun, crowded, or infested with. [old english]