n. (Gr. Myth.) A Phrygian king who was punished in the lower world by being placed in the midst of a lake whose waters reached to his chin but receded whenever he attempted to allay his thirst, while over his head hung branches laden with choice fruit which likewise receded whenever he stretched out his hand to grasp them. (Zool.) A genus of wading birds comprising the wood ibises. Tantalus's cup (Physics), a philosophical toy, consisting of a cup, within which is the figure of a man, and within the figure a siphon, the longer arm of which passes down through the bottom of the cup, and allows the escape of any liquid that may be poured in, when it reaches as high as the bend of the siphon, which is just below the level of the mouth of the figure in the cup.