Definition of overspeed in US English:

overspeed

noun

  • Excessive speed; especially the operation of an engine, vehicle, etc., at a speed higher than is safe or appropriate; an instance of this.

verb

  • 1no object To travel too quickly, especially to travel faster than permitted by law or by another authority. Also with object: to cause (a vehicle) to travel more quickly than is safe. Now chiefly in African and S. Asian use.

  • 2with object Chiefly Mechanics. To operate (an engine or other machine) at a speed higher than is safe for its gearing or other components.

Origin

Early 19th century; earliest use found in Samuel Singer (1783–1858), literary scholar. From over- + speed<br>late 17th century; earliest use found in John Evelyn (1620–1706), diarist and writer. From over- + speed.

Pronunciation

overspeed

/ˌəʊvəˈspiːd/