A small rodent with a pointy face, rounded ears, and a long tail is called a mouse. A mouse may be kept as a pet, or it may be an uninvited guest in your home.
A person who is timid and shy can also be called a mouse. In computer terms, a mouse is a corded or wireless device that moves your computer's cursor while you move the mouse. In most cases, the plural of mouse is "mice," but more than one computer mouse can also be called "mouses." Mouse can also be a verb in this context, like when you mouse over an icon to select a link.