step in

名词 step in:

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

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, interfere, interpose
2. act as a substitute
   同义词：substitute, deputize, deputise

1. A well-tied tie is a first serious step in life.
   结得整整齐齐的领带，是人生严肃的第一步。
2. If the police had not stepped in when they did there would have been serious violence.
   当时若警方迟一些干预就会发生严重的暴力事件了。
3. I asked him why he didn't step in and help stop the argument.
   我问他，为什么他不进行干预，制止这场争论。
4. If they step in where they're not wanted, they'll get their noses put out of joint.
   如果他们介入与他们无关的事，会有人阻止他们的。