hydraulic UK /haɪˈdɹɒlɪk/US /haɪˈdɹɔːlɪk/adjective 3verb 1forms 3 adjective3 •Pertaining to water. •Related to, or operated by, hydraulics.A hydraulic press is operated by the differential pressure of water on pistons of different dimensions. •Able to set underwater.hydraulic gypsum; hydraulic cements verb1 •To mine using the technique of hydraulic mining. formshydraulicked · hydraulicking · hydraulics