名詞 step in:

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

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, interfere, interpose
2. act as a substitute
   同義詞：substitute, deputize, deputise

1. A well-tied tie is a first serious step in life.
   結(jié)得整整齊齊的領(lǐng)帶，是人生嚴肅的第一步。
2. If the police had not stepped in when they did there would have been serious violence.
   當時若警方遲一些干預(yù)就會發(fā)生嚴重的暴力事件了。
3. I asked him why he didn't step in and help stop the argument.
   我問他，為什么他不進行干預(yù)，制止這場爭論。
4. If they step in where they're not wanted, they'll get their noses put out of joint.
   如果他們介入與他們無關(guān)的事，會有人阻止他們的。