Definition of hydraulic in English:


Pronunciation /hʌɪˈdrɒlɪk//hʌɪˈdrɔːlɪk/


  • 1Denoting or relating to a liquid moving in a confined space under pressure.

    ‘hydraulic fluid’
    • ‘A clean machine is a healthy machine, and a variety of items can contaminate hydraulic oil.’
    • ‘They were looking for rust, metal shavings, hydraulic oil, etc. that might get on the chickens, thus contaminating them.’
    • ‘When putting away tractors and combines for the winter, take engine and hydraulic oil samples and submit for oil analysis.’
    • ‘This pressurised hydraulic fluid is under the control of an electric solenoid or motor operated valve to achieve the force and position required each time a clutch and/or gear change is needed.’
    • ‘The best time to change hydraulic oil is at the end of the season when contaminants, such as water and dust, are in suspension.’
    • ‘Remote drains for engine oil, hydraulic oil, and engine coolant are grouped in one location for convenience.’
    • ‘Nor did they first pump out all the hydraulic oils and hazardous chemicals, nor cut away potentially dangerous protuberances.’
    • ‘Checking my hydraulic and brake pressure gauges, I saw the systems were operating normally.’
    • ‘Earth movers, excavators, backhoes, and bulldozers rely on hydraulic fluids to lift, move, scrape, and dig.’
    • ‘In the first response stage, the brake pads are placed on the brake disc and the hydraulic pressure increased without initiating braking.’
    • ‘Also helpful for operators in hot climates is the substitution of hydraulic oil for normal formula.’
    • ‘The bypass control cylinders automatically bypassed the hydraulic fluid through the actuating cylinder when hydraulic pressure was lost.’
    • ‘Until now, conventional hydraulic oil would break down sooner, leaving your machine's metal abrasively scraping against metal.’
    • ‘That includes using non-toxic hydraulic oils for his machinery, and synthetic engine oils all around in the hopes of reducing maintenance downtime.’
    • ‘Adequate hydraulic oil flow to the grapple saw has been another problem with a retrofitted attachment.’
    • ‘Possible sheet metal damage was also noticed on the left side of the retardant tank and hydraulic oil was seeping from this point.’
    • ‘This pump uses rotating gear assemblies within a pump housing to produce the hydraulic oil flow.’
    • ‘Never leave the machine parked with booms or arches suspended off the ground, as they will inject hydraulic oil into the fire if a supporting hose burns through.’
    • ‘To raise the capsule through the water, pumps shift about a cup of hydraulic oil from a reservoir in the cylinder to a small external bladder.’
    • ‘After we shot down the catapult, we saw a sheen of hydraulic fluid covering the pressure bulkhead in the back of the aircraft.’
  • 2Relating to the science of hydraulics.

    ‘hydraulic analysis of streams’
    • ‘Anatomical measurements were done on samples previously used for the analysis of hydraulic parameters.’
    • ‘The eleven imperial water mill visits testify to the founders' keen interest in the science of hydraulic engineering.’
    • ‘The same is true of the hydraulic and equilibrium notions drawn from other sciences.’
    • ‘Mitchell reports that further hydraulic analysis will be conducted within the next two weeks by the Water Resources Hydrology department.’
    • ‘Following the investigation, a hydraulic analysis of sewers is due to take place.’
  • 3(of cement) hardening under water.

    • ‘If you see cracks in the walls leaking, some of these can be repaired with hydraulic cement or crack injection.’
    • ‘Nevertheless, Henry knew research was expected of him, and he began investigating the chemical reactions involved in the setting of hydraulic cements.’


Early 17th century: via Latin from Greek hudraulikos, from hudro- ‘water’ + aulos ‘pipe’.