vespertilian bat

NOUN
16 LETTERS · STARTS WITH V

vespertilian bat is a valid 16-letter word worth 22 points in Scrabble and 27 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
V4E1S1P3E1R1T1I1L1I1A1N1B3A1T1
4 + 1 + 1 + 3 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 0 + 3 + 1 + 1 =22 PTS
DOUBLE WORD → 44TRIPLE WORD → 66
MEANING

What does vespertilian bat mean?