A galoot is a clumsy, foolish, or silly person. If your brother stumbles and drops an entire pizza on the kitchen floor, you'll be tempted to call him a galoot.
Galoot is an informal word for a fool or a goofy guy. Many TV and film comedies feature a character who's a galoot, someone to laugh at for his stupidity or clumsiness. This word is used in both the US and Scotland, and its origin is uncertain, although it most likely began as nautical slang for "green" or new sailors, especially if they were marines or soldiers.