Definition - What does Squick mean?
Squick is a term used to describe the uncomfortable feeling that some people may have when they hear about or see certain kinky acts. This can apply to acts such as bondage, whipping, caning, scat play, and blood play just to name a few. It's a term that has been adopted by the BDSM community to describe acts that elicit a gut reaction of repulsion without making any moral judgment about the activity.
Kinkly explains Squick
Many believe that the term squick is actually a combination of the words "squirm" and "ick." It's used when talking about an act that makes one squirm because of the ick-factor. Of course, this is highly personal, as everyone has their own squicks; what turns one person on may squick another. Squick is used in place of the word "disgust" which implies a moral repugnance to an act.