1. 争吵;争执
A run-in is an argument or quarrel with someone.
e.g. I had a monumental run-in with him a couple of years ago.
几年前，我和他大吵了一架。
2. 赛前期;预赛;热身赛
The run-in to a sporting event is the period of time or series of matches leading up to it.
e.g. If Bob is at his best, we'll be able to win the most difficult game of our run-in.
只要鲍勃处于最佳状态，我们就能拿下最艰难的一场预赛。