What does "titmouse" mean?

Titmouse: Any one of numerous species of small insectivorous singing birds belonging to Parus and allied genera; -- called also tit, and tomtit. Note: The blue titmouse (Parus coeruleus), the marsh titmouse (P. palustris), the crested titmouse (P. cristatus), the great titmouse (P. major), and the long tailed titmouse (Ægithalos caudatus), are the best-known European species. See Chickadee.