a person who makes (often derisive) sounds when communicating that sound like "sssshh", "tsssss", chsssh" "pssss", similar to the sound of hydraulic brakes on a truck. A person who makes these sounds is said to be a member of "hydraulic nation".
Did you hear what he said? tssss. (observer) Another member of hydraulic nation.
by Kurt W November 27, 2007