soundonce <sound number>
soundoncevar <sound number>
Plays the sound <sound number> as defined by definesound the same way that the sound command does, except that the same sound may not begin playing again until the current instance of it (from any actor) has finished.
Commands with an additional "var" suffix take gamevars rather than constants or defined labels for their inputs. As an alternate short form, "varvar" can be dropped from these commands; for example ife serves an an alias for ifvarvare.