4. Motion with reference to direction
[Motion downwards] Descent.
[Nouns] descent, descension, declension, declination; fall; falling: slump; drop, plunge, plummet, cadence; subsidence, collapse, lapse; downfall, tumble, slip, tilt, trip, lurch; cropper, culbute; titubation, stumble; fate of Icarus.
avalanche, debacle, landslip, landslide.
declivity, dip, hill.
[Verbs] descend; go down, drop down, come down; fall, gravitate, drop, slip, slide, settle; plunge, plummet, crash; decline, set, sink, droop, come down a peg; slump.
tumble, trip, stumble, titubate, lurch, pitch, swag, topple, topple over, tumble over, topple down, tumble down; tilt, sprawl, plump down, come down a cropper.