steepen
verb uk/ˈstiː.pən/ us/ˈstiː.pən/
[ I or T ]（使）变陡
to become steeper, or to make something do this
The trail began to steepen near the top of the hill. 小路在接近山顶时开始变陡。
[ I ]（费用等）增加
If something such as a cost steepens, it increases.
Our costs have steepened since we began this project. 自从开始了这个项目，我们的费用就增加了。