1. A very small rodent which has a pointed nose and a long thin tale: The house was invaded by mice and it didn't take long before one of the many traps caught and killed one of them.
2. A shy, inconspicuous, unobtrusive person: Poor Susan, she is such a mouse at parties and even when she is in a group with other people.

When referring to the computer tool, a small tool which is used to move with the hand to control functions: Mike used the hand-operated electronic mouse to control the coordinates on his computer screen while he moved it around on a pad.

Actually, Mike had two different mouses, one with a connecting cord and one which was cordless.

1. To hunt for small rodents which are pests with the intention of killing them: During the winter, Joshua spent a lot of time mousing in his garage.
2. To look for, to hunt for something, or someone in a quiet, stealthy manner: The cats moused around the barn looking for small rodents.
3. Using a hand-held computer device to control the movement of a pointer on the computer screen which, when rolled along a flat surface, directs an indicator to move correspondingly around a computer screen, allowing the operator to move the indicator freely so he or she can select operations or manipulate text or graphics: While the technicians were mousing around on the new computer, they were able to determine if the quality had really improved as claimed by the computer company.

Thomas is a person who mouses for hours at a time at work and at home; in fact, his wife once told a friend that they both mouse on their separate computers.