Wiktionary
n. An artificially created or enhanced sound, used to accompany the action of a dramatic production, such as a film, play or video game
WordNet
n. an effect that imitates a sound called for in the script of a play
Wikipedia
Sound effects (or audio effects) are artificially created or enhanced sounds, or sound processes used to emphasize artistic or other content of films, television shows, live performance, animation, video games, music, or other media. In motion picture and television production, a sound effect is a sound recorded and presented to make a specific storytelling or creative point without the use of dialogue or music. The term often refers to a process applied to a recording, without necessarily referring to the recording itself. In professional motion picture and television production, dialogue, music, and sound effects recordings are treated as separate elements. Dialogue and music recordings are never referred to as sound effects, even though the processes applied to such as reverberation or flanging effects, often are called "sound effects".
Usage examples of "sound effect".
When the cryptogram on the paper tape announced a base hit, he would whack the edge of the table with a pencil, creating a little sound effect, and describe the arc of the ball as if he could actually see it.
These are guys whose superpowers can be more a nuisance than an asset, guys like Sound Effect Man, a second-banana superhero if ever there was one.
She opened and closed a dresser drawer for the sound effect, then plastered a smile on her face and stepped to the door.
Gramps made an appropriate sound effect by sucking air wetly through his teeth, and chuckled.