Decrease and Slump

decrease

A change downward.
- usage: "there was a decrease in his temperature as the fever subsided"; "there was a sharp drop-off in sales"
- synonyms: lessening, drop-off
A process of becoming smaller or shorter.
- synonyms: decrement
The amount by which something decreases.
- synonyms: decrement
The act of decreasing or reducing something.
- synonyms: diminution, reduction, step-down

Decrease in size, extent, or range.
- usage: "The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fell to under a hundred pounds"; "his voice fell to a whisper"
- synonyms: diminish, lessen, fall
Make smaller.
- usage: "He decreased his staff"
- synonyms: lessen, minify

(v.t.) To cause to grow less; to diminish gradually; as, extravagance decreases one's means.
(v.) A becoming less; gradual diminution; decay; as, a decrease of revenue or of strength.
(n.) To grow less, -- opposed to increase; to be diminished gradually, in size, degree, number, duration, etc. or in strength, quality or excellence; as, they days decrease in length from June to December.
(v.) The wane of the moon.

Webster's Revised Unabridged Dictionary

slump

A noticeable deterioration in performance or quality.
- usage: "the team went into a slump"; "a gradual slack in output"; "a drop-off in attendance"; "a falloff in quality"
- synonyms: slack, drop-off, falloff, falling off
A long-term economic state characterized by unemployment and low prices and low levels of trade and investment.
- synonyms: depression, economic crisis

Assume a drooping posture or carriage.
- synonyms: slouch
Fall or sink heavily.
- usage: "He slumped onto the couch"; "My spirits sank"
- synonyms: slide down, sink
Fall heavily or suddenly; decline markedly.
- usage: "The real estate market fell off"
- synonyms: fall off, sink
Go down in value.
- usage: "the stock market corrected"; "prices slumped"
- synonyms: decline, correct

(v.i.) To undergo a slump or sudden decline or falling off; as, the stock slumped ten points.
(n.) A falling or declining, especially suddenly and markedly; a falling off; as, a slump in trade, in prices, etc.
(v.i.) To slide or slip on a declivity, so that the motion is perceptible; -- said of masses of earth or rock.
(n.) The noise made by anything falling into a hole or into a soft, miry place.
(v.t.) To lump; to throw into a mess.
(v.i.) 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.
(n.) A boggy place.
(n.) The gross amount; the mass; the lump.

Webster's Revised Unabridged Dictionary

Slump is a temporary fall in performance, often describing consistently falling security prices for several weeks or months.