hexagonal nipple

hexagonal nipple

[‚hek¦sag·ən·əl ′nip·əl]
(design engineering)
A nipple for joining pipe with a hexagonal configuration around the center of the exterior surface to permit tightening with a spanner.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.