To sing (a note or song, for example) with trills, runs, or other melodic embellishments. To sing with trills, runs, or quavers. To be sounded in a trilling or quavering manner. The act or an instance of singing with trills, runs, or quavers. An abscessed boillike swelling on the back of cattle, deer, and certain other animals, caused by the larva of a warble fly. The warble fly, especially in its larval stage. A hard lump of tissue on a riding horse's back caused by rubbing of the saddle.