steepening

verb

1. (form-of, gerund, participle, present)Present participle and gerund of steepen.

   “All three parallel valleys of the Llynvi, Garw and Ogmore are much the same in physical character: the lower reaches are wooded and not unattractive, but as the railway climbs on ever-steepening grades, the hills on either hand grow barer and closer together, while in all respects the scene becomes more sombre, with the terraced, slate-roofed colliery towns and the road, railway and river all struggling for space in the narrowing defiles.”

noun

1. The process of becoming steeper.