CEDICT
abnormal rotational alignments of the legs, resulting in a 八-shaped appearance of the feet when standing, which can be either toes closer together (內八字) or toes farther apart (外八字)
Wiktionary
形容人走路，雙腳撇開如同八字。一般有內、外八字之分。
重編國語辭典
classifiers: 雙, 隻