From Longman Business Dictionary
slumpslump /slʌmp/ noun [countableC usually singular]1a sudden fall in the price, value, or number of somethingslump inThere has been a slump in sales this month.
2ECONOMICS a period of time when there is a big reduction in economic activity, forcing many companies to close and many people to lose their jobsSavings were already extremely low at the beginning of the current slump.
—slump verb [intransitiveI]Securities firms’ profits have slumped in recent years.