steepening

/S T IY1 P AH0 N IH0 NG/
verb
  1. 1

    To make steeper.

  2. 2

    To become steeper.

noun
  1. 1

    The process of becoming steeper.

Source: https://en.wiktionary.org/wiki/steepen, https://en.wiktionary.org/wiki/steepening