Definition of training wheel in English:

training wheel

noun

  • 1A wheel that is turned in order to train a cannon or other firearm. Now historical.

  • 2Chiefly North American. In plural A pair of small wheels fitted one on either side of the rear wheel of a bicycle, to add stability when learning to ride.

Origin

Mid 19th century (in an earlier sense).

Pronunciation

training wheel

/ˈtreɪnɪŋ wiːl/