/klep"si dreuh/ , n. , pl. clepsydras, clepsydrae /-dree'/ .
an ancient device for measuring time by the regulated flow of water or mercury through a small aperture.
[ 1640-50; klepsýdra, equiv. to kleps- ( klep-, s. of kléptein to steal, conceal + -s- formative in derivation) + hydra, deriv. of hýdor water ]