mouse 
(mous)
(mous)n. pl. mice (mīs)
1.
a. Any of numerous small rodents of the families Muridae and Cricetidae, such as the house mouse, characteristically having a pointed snout, small rounded ears, and a long naked or almost hairless tail.
b. Any of various similar or related animals, such as the jumping mouse, the vole, or the jerboa.
2. A cowardly or timid person.
3. Informal A discolored swelling under the eye caused by a blow; a black eye.
4. pl. mice or mous·es (mousĭz) Computers A handheld, button-activated input device that when rolled along a flat surface directs an indicator to move correspondingly about a computer screen, allowing the operator to move the indicator freely, as to select operations or manipulate text or graphics.
intr.v. (mouz, mous) moused, mous·ing, mous·es
Phrasal Verb: 1. To hunt mice.
2. To search furtively for something; prowl.
mouse over
To hold a computer pointer over (a particular object or area of a screen) so as to cause a pop-up box to appear or other change to occur.
[Middle English mous, from Old English mūs; see mūs- in the Appendix of Indo-European roots.]