Any of various semiaquatic and chiefly tropical rodents of the family Muridae, especially of the Australasian genera Hydromys and Xeromys and the Central American genus Rheomys.
Origin
Late Middle English (in an earlier sense). From water + mouse.
Definition of water mouse in US English:
water mouse
nounˈwɔːtə ˌmaʊs
Any of various semiaquatic and chiefly tropical rodents of the family Muridae, especially of the Australasian genera Hydromys and Xeromys and the Central American genus Rheomys.
Origin
Late Middle English (in an earlier sense). From water + mouse.