Schlick, or schlicking, is the sound supposedly made when a girl/woman masturbates. Urban Dictionary has recorded its usage as a slang since 2003.
The name derived from Japanese comics not long after the word FAP was invented (Fap is the word used for male masturbation sounds in Japanese comics).
-SHLICK SHLICK SHLICK-
Shanon Lee: Ahhhh.. that felt great!