= H =
[very common] Hardware or software
activity designed to start or keep two machines or programs in
synchronization as they do protocol. Often applied to human
activity; thus, a hacker might watch two people in conversation
nodding their heads to indicate that they have heard each others'
points and say "Oh, they're handshaking!". See also
--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.