as a warning or signal , typically consisting of a rotating perforated metal drum through which air or steam is passed under pressure sometimes capital ( greek mythology ) one of several sea nymphs whose seductive singing was believed to lure sailors to destruction on the rocks the nymphs inhabited any aquatic eel-like salamander of the north american family sirenidae , having external gills , no hind limbs , and reduced forelimbs something was not quite right behind the reception desk .