Something that's done in a snobby, stuck-up way is done superciliously. Superciliously commenting that your friend's house is the smallest you've ever seen isn't likely to get you invited back.
People who act superciliously appear to think that they're better — smarter, more savvy, wealthier — than everyone else. You might superciliously ask your taxi driver if he's unfamiliar with the city, or glance superciliously at a couple of giggling teenagers in line at the movies. The word comes from its related adjective, supercilious, which has a Latin root, supercilium, used to mean "haughty demeanor or pride," but literally meaning "eyebrow," as when a supercilious person raises one haughty eyebrow.