Definition of: vireo

(vir′ē·ō) noun plural ·os
Any of various small, insectivorous birds (family Vireonidae), predominantly dull–green and grayish, which make slight, cup–shaped, pensile nests; a greenlet. The red–eyed vireo (Vireo olivaceus), the yellow–throated vireo (V. flavifrons), the white–eyed vireo (V. griseus), the blue–headed or solitary vireo (V. solitarius) and the warbling vireo (V. gilvus) are common in the United States. Many of the species are noted for their song. [<L, a kind of small bird,? the greenfinch]