adj. 1 (of water, oil, etc.) conveyed through pipes or channels usu. by pressure. 2 (of a mechanism etc.) operated by liquid moving in this manner (hydraulic brakes; hydraulic lift). 3 of or concerned with hydraulics (hydraulic engineer). 4 hardening under water (hydraulic cement). hydraulic press a device in which the force applied to a fluid creates a pressure which when transmitted to a larger volume of fluid gives rise to a greater force. hydraulic ram an automatic pump in which the kinetic energy of a descending column of water raises some of the water above its original level. hydraulically adv. hydraulicity n.
[ L hydraulicus f. Gk hudraulikos f. hudor water + aulos pipe ]