step-in

名词 step-in:

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

动词 step-in:

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