fade out

Short definition from Wiktionary

Noun

1. 1
   A type of transition used in film, usually at the end of a scene, involving a fade to black from the cut.
2. 2
   Alternative form of fadeout.

Verb

1. 1
   To slowly disappear; to wither away.
2. 2
   To sneak away.
3. 3
   To fade from a cut to black in a movie.
4. 4
   To decrease in volume, such as at the end of a song, until there is only silence.