名詞 step-in:

1. short underpants for women or children (usually used in the plural)
   同義詞：pantie, panty, scanty

動詞 step-in:

1. get involved, so as to alter or hinder an action, or through force or threat of force
   同義詞：intervene, step in, interfere, interpose
2. act as a substitute
   同義詞：substitute, deputize, deputise, step in