Mutt has more than one meaning:

• When referring to a dog, mutt means a mixed-breed dog with parents from different breeds.
• Mutt is sometimes used informally to refer to mixed breeding of other species as well.
• Mutt (email client) is a terminal-based email client for Unix systems.
• Mutt was a character in the Mutt and Jeff comic strip.
• A mutt is a type of Hindu monastery.