The Collaborative International Dictionary
Ground joint
ground \ground\,
imp. & p. p. of Grind.
[1913 Webster] ground cock, a cock, the plug of which is
ground into its seat, as distinguished from a compression
cock.
--Knight. Ground glass, glass the transparency of
which has been destroyed by having its surface roughened
by grinding. -- Ground joint, a close joint made by
grinding together two pieces, as of metal with emery and
oil, or of glass with fine sand and water.