any of a genus (Pipistrellus) of small bats that characteristically fly early in the evening: found in North America and in most of the Eastern Hemisphere
See pipistrelle in American Heritage Dictionary 4
also pip·i·strel(pĭpˌĭ-strĕlˈ, pĭpˈĭ-strĕlˌ)
noun
Any of various very small insectivorous bats of the genus Pipistrellus, found throughout the world.