slump 
(slŭmp)
(slŭmp)intr.v. slumped, slump·ing, slumps
1. To fall or sink heavily; collapse: She slumped, exhausted, onto the sofa.
2. To droop, as in sitting or standing; slouch.
3.
a. To decline suddenly; fall off: Business slumped after the holidays.
b. To perform poorly or inadequately: The team has been slumping for a month.
4.
a. To sink or settle, as into mud or slush.
b. To slide down or spread out thickly, as mud or fresh concrete.
n.
1. The act or an instance of slumping.
2. A drooping or slouching posture: read defeat in the slump of his shoulders.
3. A sudden falling off or decline, as in activity, prices, or business: a stock market slump; a slump in farm prices.
4. An extended period of poor performance, especially in a sport or competitive activity: a slump in a batting average.
5. See grunt.
[Probably of Scandinavian origin; akin to Norwegian slumpa, to slump.]