thin out

verb2

1. •
   To make sparse; to remove some of a group of newly-planted plants in order to allow the remaining ones to grow unimpeded.
2. •
   To become sparse.

   • And later on, when the crowd thinned out / I was just about to do the same / She was standing there in back of my chair / Said to me, "Don't I know your name?" — 1975