Available Definitions:
1) n. - Music sung or performed in the open air at nights; -- usually applied to musical entertainments given in the open air at night, especially by gentlemen, in a spirit of gallantry, under the windows of ladies.
2) n. - A piece of music suitable to be performed at such times.
3) v. t. - To entertain with a serenade.
4) v. i. - To perform a serenade.