Sing  —v. (past sang; past part. Sung) 1 utter musical sounds, esp. Words with a set tune. 2 utter or produce by singing. 3 (of the wind, a kettle, etc.) Hum, buzz, or whistle. 4 (of the ears) hear a humming sound. 5 slang turn informer. 6 (foll. By of) literary celebrate in verse. —n. Act or spell of singing.  sing out shout. Sing the praises of praise enthusiastically.  singer n. [old english]