from
The Collaborative International Dictionary of English v.0.48
Slump \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.]
1. 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.
[1913 Webster]
The latter walk on a bottomless quag, into which
unawares they may slump. --Barrow.
[1913 Webster]
2. To slide or slip on a declivity, so that the motion is
perceptible; -- said of masses of earth or rock.
[Webster 1913 Suppl.]
3. To undergo a slump, or sudden decline or falling off; as,
the stock slumped ten points. [Colloq.]
[Webster 1913 Suppl.]