SLUMP (3)
Source: 567
Slump, v. i. [imp. & p. p. Slumped (?); p. pr. & vb. n. Slumping.] [[Scot. slump a dull noise produced by something falling into a hole, a marsh, a swamp.]] To fall or sink suddenly through or in, when walking on a surface, as on thawing snow or ice, partly frozen ground, a bog, etc., not strong enough to bear the person. The latter walk on a bottomless quag, into which unawares they may slump. Barrow.