To become steeper, or to make something steeper. A slope, a road, a hill, a path — it starts gentle and then goes up (or down) at a sharper angle. The word works two ways. It can be intransitive, with the slope doing it by itself: 'The road steepens after the bridge.' Or transitive, with someone or something causing it: 'They steepened the ramp to save space.' The intransitive use is much more common in real writing. You will meet this word most in walking, cycling and climbing talk, and in geography lessons. It is a fairly formal, written word — a hiker chatting to a friend would more likely say 'it gets steeper' or 'it really goes up here'. Writers also stretch it beyond hills, to any line on a graph that rises faster: prices, temperatures, a curve on a chart. 'The curve steepens after 2010' means the numbers started climbing more sharply. That graph use is quite common in news and science writing, so it is worth knowing.

變陡；使變陡（山路、坡度）。用在圖表上時是「曲線變得更陡」，中文常說「陡升」或「斜率變大」