1. To slant toward or recede from something at a downward angle. The field slopes down from the mansion at the top, forming something of shallow basin below. The driveway slopes down to the main road at a sharp angle, so you've got to be careful to always have your handbrake on when you park your car out there.

2. To cause or construct something to slant toward or recede from something at a downward angle. In this usage, a noun or pronoun can be used between "slope" and "down." Tell the landscapers to slope the grass down to the road to help rainwater naturally drain off into the gutters. Whoever built this bookshelf obviously wasn't paying attention, because they sloped all the shelves slope down from the back of it, so things keep rolling off and breaking on the ground!