Swim  —v. (-mm-; past swam; past part. Swum) 1 propel the body through water with limbs, fins, or tail. 2 traverse (a stretch of water or distance) by swimming. 3 perform (a stroke) by swimming. 4 float on a liquid. 5 appear to undulate, reel, or whirl. 6 feel dizzy (my head swam). 7 (foll. By in, with) be flooded. —n. Period or act of swimming.  in the swim colloq. Involved in or aware of what is going on.  swimmer n. [old english]