Of ground: To swell through excess of moisture; to slip or run when left unsupported.

To slide off heavily; to plump down; to fall or collapse clumsily or heavily. spec. in Geomorphology of soil, sediment, etc.: to fall in a slump…

Of soil, talus, etc.: to undergo creep (sense 6a); to move imperceptibly en masse.

intransitive. To move slowly by solifluction.