A futuristic slang word used in the Otherland book series, written by Tad Williams. It is used in a similar way to suck, and is possibly an abbreviation of scandalous. However, scan can mean anything from tease to creep out.
What a squeamish person does when presented with something which they don't like, especially blood, gore, maggots, spiders, and so on. To squeam generally means to be horrified, and to wriggle, squeal, scream, make other high-pitched noises.
Harry made the girls squeam by dropping worms down their blouses.
The ant crawling up Cindy's leg made her squeam with all her might.