Definition of "rein in"

rein in

verb
third-person singular simple present reins in, present participle reining in, simple past and past participle reined in
1. To stop or slow a horse by pulling the reins
2. (figurative) To stop or slow something, by exercising control.
  Quotations
  “As you are well aware, over the last few months we’ve made a considerable effort to rein in costs, but it simply hasn’t been enough,” Daniel Ek, Spotify’s chief executive, said in a note to employees on Monday.
  2023 January 23, Isabella Simonetti, quoting Daniel Ek, “Spotify to Lay Off 6% of Its Work Force”, in The New York Times‎