The noun guise refers to an outward appearance that conceals the true nature of someone or something. Your classmate might chat with you under the guise of friendship, but you know she's really just looking for juicy gossip.
No doubt you’ve noticed the similarity between guise and disguise. Both involve the art of deception: it’s the methods that differ. Guise is about trying on new attitudes and mannerisms, such as speaking and acting in the guise of a native in a place where you are actually a tourist. Disguise involves hiding your real identity, disappearing in the new role.