Definition of vespertilio
1 capitalized : the type genus of Vespertilionidae formerly comprehensive but now comprising solely the frosted bat (V. murinus) or slightly extended to include the serotine and the American brown bats which are more often placed in the genus Eptesicus
2 plural -s : any bat of the genus Vespertilio; broadly : bat
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Origin and Etymology of vespertilio
New Latin, from Latin, bat, from vesper evening — more at west
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