thinning out

Verb

thin out (third-person singular simple present thins out, present participle thinning out, simple past and past participle thinned out)

1. (transitive) To make sparse; to remove some of a group of newly-planted plants in order to allow the remaining ones to grow unimpeded.
2. (intransitive) 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, Bob Dylan, “Tangled Up in Blue”, in Blood on the Tracks