define swell.
(swÉl) v. swelled, swolâ¢len swelled, swellâ¢ing, v.i. 1. to enlarge in bulk, as by growth, absorption of fluid, or engorgement. 2. (of a body part or area) to enlarge abnormally without growth of tissue. 3. to rise in waves, as the sea. 4. to well up, as a spring or as tears.