Wiktionary
training wheel
alt. 1 (context rare English) One of a pair of training wheels: small wheels placed on either side of a bicycle's wheel to provide support for new riders. 2 Anything designed to support a tyro. n. 1 (context rare English) One of a pair of training wheels: small wheels placed on either side of a bicycle's wheel to provide support for new riders. 2 Anything designed to support a tyro.