1. rapidity in moving, going, traveling, proceeding, or performing; swiftness; celerity: the speed of light; the speed of sound.
  2. relative rapidity in moving, going, etc.; rate of motion or progress: full speed ahead.
  3. full, maximum, or optimum rate of motion: The car gets to speed in just nine seconds.
  4. Automotive. a transmission gear ratio.
  5. Photography.
    1. Also called film speed.the sensitivity of a film or paper to light, measured by an ASA or DIN index, which assigns low numbers to slow film and higher numbers to faster film.
    2. Also called shutter speed.the length of time a shutter is opened to expose film.
    3. the largest opening at which a lens can be used.
  6. Slang. a stimulating drug, as caffeine, ephedrine, or especially methamphetamine or amphetamine.
  7. Informal. a person or thing that is compatible with or typical of one’s ability, personality, desires, etc.: My speed is writing postcards on the porch while everyone else is tearing around the tennis court.
  8. Archaic. success or prosperity.

verb (used with object), sped or speed·ed, speed·ing.

  1. to promote the success of (an affair, undertaking, etc.); further, forward, or expedite.
  2. to direct (the steps, course, way, etc.) with speed.
  3. to increase the rate of speed of (usually followed by up): to speed up industrial production.
  4. to bring to a particular speed, as a machine.
  5. to cause to move, go, or proceed with speed.
  6. to expedite the going of: to speed the parting guest.
  7. Archaic. to cause to succeed or prosper.

verb (used without object), sped or speed·ed, speed·ing.

  1. to move, go, pass, or proceed with speed or rapidity.
  2. to drive a vehicle at a rate that exceeds the legally established maximum: He was arrested for speeding.
  3. to increase the rate of speed or progress (usually followed by up).
  4. to get on or fare in a specified or particular manner.
  5. Archaic. to succeed or prosper.


  1. at full/top speed,
    1. at the greatest speed possible: We drove down the highway at full speed.
    2. to the maximum of one’s capabilities; with great rapidity: He worked at full speed.
  2. up to speed,
    1. operating at full or optimum speed.
    2. functioning or producing at an expected, acceptable, or competitive level; up to par: a new firm not yet up to speed.


  1. the act or quality of acting or moving fast; rapidity
  2. the rate at which something moves, is done, or acts
  3. physics a scalar measure of the rate of movement of a body expressed either as the distance travelled divided by the time taken (average speed) or the rate of change of position with respect to time at a particular point (instantaneous speed). It is measured in metres per second, miles per hour, etc
  4. a rate of rotation, usually expressed in revolutions per unit time
    1. a gear ratio in a motor vehicle, bicycle, etc
    2. (in combination)a three-speed gear
  5. photog a numerical expression of the sensitivity to light of a particular type of film, paper, or plateSee also ISO rating
  6. photog a measure of the ability of a lens to pass light from an object to the image position, determined by the aperture and also the transmitting power of the lens. It increases as the f-number is decreased and vice versa
  7. a slang word for amphetamine
  8. archaic prosperity or success
  9. at speed quickly
  10. up to speed
    1. operating at an acceptable or competitive level
    2. in possession of all the relevant or necessary information

verb speeds, speeding, sped or speeded

  1. to move or go or cause to move or go quickly
  2. (intr) to drive (a motor vehicle) at a high speed, esp above legal limits
  3. (tr) to help further the success or completion of
  4. (intr) slang to take or be under the influence of amphetamines
  5. (intr) to operate or run at a high speed
  6. archaic
    1. (intr)to prosper or succeed
    2. (tr)to wish success to

n.Old English sped “success, prosperity, advancement,” from Proto-Germanic *spodiz (cf. Old Saxon spod “success,” Dutch spoed “haste, speed,” Old High German spuot “success,” Old Saxon spodian “to cause to succeed,” Middle Dutch spoeden, Old High German spuoten “to haste”), from PIE *spo-ti- “speed,” from *spe- “to thrive, prosper” (cf. Sanskrit sphayate “increases,” Latin sperare “to hope,” Old Church Slavonic spechu “endeavor,” Lithuanian speju “to have leisure”). Meaning “quickness of motion or progress” emerged in late Old English (usually adverbially, in dative plural, e.g. spedum feran), emerging fully in early Middle English. Meaning “gear of a machine” is attested from 1866. Meaning “methamphetamine, or a related drug,” first attested 1967, from its effect on users. Speed bump is 1975; figurative sense is 1990s. Full speed is recorded from late 14c. Speed reading first attested 1965. Speedball “mix of cocaine and morphine or heroin” is recorded from 1909. v.Old English spedan “to succeed, prosper, advance” (see speed (n.)). Meaning “to go fast” is attested from c.1300. Meaning “to send forth with quickness” is first recorded 1560s; that of “to increase the work rate of” (usually with up) is from 1856. Related: Speeded; speeding.

  1. The ratio of the distance traveled by an object (regardless of its direction) to the time required to travel that distance. Compare velocity.

In addition to the idiom beginning with speed

  • speed up
  • also see:

  • full speed ahead
  • up to par (speed)
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