Steep means sharply angled. When hiking trails lead straight up mountainsides, they've got a steep incline. Steep also means "to soak in," as in steeping a tea bag in boiling water.
You often hear steep used as an adjective to describe cliffs, hills, or even water park slides that have a perilous slope. Steep can apply to curves on a chart––you might say when someone who has a lot to learn that their learning curve is going to be steep. Steep also comes up to describe exorbitant changes in costs or spending. Everyone would love to travel more, but sometimes plane fare is too steep.