Definition of valve in US English:



  • 1A device for controlling the passage of fluid or air through a pipe, duct, etc., especially an automatic device allowing movement in one direction only.

    ‘a valve shuts off the flow from the boiler when the water is hot enough’
    • ‘On offer is a 3 litre petrol engine V6 with four valves per cylinder.’
    • ‘If the burner doesn't ignite quickly, shut off the valves, leave the lid open and allow the grill to air out for several minutes before you try to light it again.’
    • ‘The required ingredients are then pumped from their storage areas through a series of valves and pipes that eventually lead to the blend tanks.’
    • ‘For example, every fixture must include an isolation valve to allow maintenance personnel to shut down individual fixtures.’
    • ‘Multifunctional tools, such as graders, require an electrical outlet and switches on the loader to control hydraulic diverter valves.’
    • ‘To remove the clog, close the shutoff valve at the bottom of the radiator and unscrew the air vent.’
    • ‘Its speed can be influenced by the waste-gate valve, which is controlled by the pressure-driven converter.’
    • ‘All control valves are located on the left side of the machine for convenience.’
    • ‘The patented sensitive microphone detects the noise of a water leak transmitted along pipes, valves, and hydrants and through the ground.’
    • ‘Using them would mean that attachments could be installed without disassembly of the main control valve or draining of hydraulic fluids.’
    • ‘Such valves allow the intake of air but not the outflow.’
    • ‘If automatic valves are used, they should be controlled from a central location and be easy to override with manual controls.’
    • ‘Close the water valves and disconnect the water lines just above the valves and the drain piping at the trap.’
    • ‘The pump design accomplishes all fluid control functions while eliminating valves that can clog, fatigue, and fail, causing accuracy drifting and pump failure over time.’
    • ‘One of the safety shutoff valves had closed in the coolant system of the third engine.’
    • ‘If you choose to have a fountain in your water garden, place the control valve from the fountain assembly onto the top outlet of the pump.’
    • ‘The pipelines are controlled by computer systems, linked to sensors and automatic valves to manage the speed of flow.’
    • ‘The main tanks were fitted with simultaneously opening dump valves controlled by either pilot.’
    • ‘The system is regulated by a height control valve which allows fluid to move between spheres to keep the car level.’
    • ‘The main type of central heating system is wet - where hot water is circulated through pipes and goes to radiators with valves that control the amount of time it spends there.’
    vent, vent hole, way out, exit, egress
    View synonyms
    1. 1.1British Electronics
      short for thermionic tube
      • ‘You could even build a functional, if somewhat cumbersome, guitar amplifier with a hydraulic system replacing transistors or valves.’
      • ‘Electronic valves are no longer used and have been replaced by transistors and diodes which have a low current consumption, greater reliability and much smaller dimensions.’
      • ‘Unlike delicate solid-state circuitry, valves are incredibly robust from an electrical perspective.’
      • ‘Silicon chips transformed the then slowly evolving world of electrical circuits and valves to the vibrant and fast developing world of electronics.’
      • ‘Equipped with transistors instead of valves, it could be operated for 80 hours on four hearing aid batteries, costing 2s 6d each.’
    2. 1.2Music A cylindrical mechanism in a brass instrument that, when depressed or turned, admits air into different sections of tubing and so extends the range of available notes.
      • ‘The soloists played on natural horns, instruments that have no valves and are not as powerful as their modern descendants.’
      • ‘For trumpeters the left hand acts merely as a clamp holding the instrument whilst the three valves are operated by fingers of the right hand.’
      • ‘The later introduction of valves extended the versatility of brass instruments to cover the full chromatic scale.’
    3. 1.3Zoology Anatomy A membranous fold in a hollow organ or tubular structure, such as a blood vessel or the digestive tract, that maintains the flow of the contents in one direction by closing in response to any pressure from reverse flow.
      • ‘The condition results from problems with valves in the veins of the leg.’
      • ‘Veins become varicose when valves in the veins closest to the skin's surface don't function correctly.’
      • ‘During pregnancy, hormones relax the muscles in your digestive tract, including the valve in the esophagus.’
      • ‘If the heart valves can't open and close correctly, blood can't flow smoothly.’
      • ‘When crocodiles are completely submerged, the ears and nostrils are closed by valves, and the eyes covered by membranes.’
    4. 1.4Zoology Each of the halves of the hinged shell of a bivalve mollusk or brachiopod, or of the parts of the compound shell of a barnacle.
      • ‘The remains usually consisted of a large piece of one valve plus a fragment of the other valve attached by a virtually intact hinge.’
      • ‘Note that each shell valve is symmetrical about the midline, but the two shell valves are often unequal in size.’
      • ‘All these plates that attach to the floor of the brachial valve may have been thickened by secondary overgrowth.’
      • ‘The two shell valves would have been rigidly fixed in place, and the dorsal margin could not have been more than a poorly elastic structure, if that.’
      • ‘The brachiopods from the limestone unit are mostly preserved as shells, most with valves conjoined.’
    5. 1.5Botany Each of the halves or sections into which a dry fruit (especially a pod or capsule) dehisces.
      • ‘Dehiscence of the anther valves begins at the distal end.’
      • ‘Fruits were harvested just prior to dehiscence of the capsule valves.’
      • ‘The fruit is a small oblong capsule with two valves containing many small seeds.’
      • ‘The brush-like hairs at the end of the anther tube are not bent, and they enclose the valve.’
      • ‘As the pollinator pushes back the brush-like hairs, the valve opens releasing the pollen onto the back of the pollinator.’


Late Middle English (denoting a leaf of a folding or double door): from Latin valva.