one who, or that which, warbles; a singer; a songster; -- applied chiefly to birds.-any one of numerous species of small old world singing birds belonging to the family sylviidae, many of which are noted songsters. the bluethroat, blackcap, reed warbler (see under reed), and sedge warbler (see under sedge) are well-known species.-any one of numerous species of small, often bright colored, american singing birds of the family or subfamily mniotiltidae, or sylvicolinae. they are allied to the old world warblers, but most of them are not particularly musical.