training wheels
noun [ plural ] US uk/ˈtreɪ.nɪŋ ˌwiːlz/ us/ˈtreɪ.nɪŋ ˌwiːlz/ (UK stabilizers)
（儿童学骑自行车时安装在后轮两侧的）稳定轮
small wheels attached to each side of the back wheel of a bicycle to prevent it from falling over when a child is learning to ride it