Guise means the outward appearance someone or something presents, especially when that appearance hides the true nature underneath. When a villain in a story appears in the guise of a helpful stranger, they're pretending to be friendly while secretly planning something harmful. When a difficult assignment comes in the guise of a fun activity, it looks entertaining at first but turns out to be serious work.

The word often suggests disguise or deception. A spy might operate under the guise of being a regular tourist, carrying a camera and guidebook while actually gathering secret information. A bully might approach someone under the guise of friendship, acting nice at first to gain trust.

You might hear people say that something happened “under the guise of” helping, when the real purpose was different. For example, someone might reorganize your desk under the guise of being helpful, when they're really just being nosy.

It's the mask something wears, the costume it puts on, the way it wants you to see it rather than what it truly is.