free fall

(noun) the ideal falling motion of something subject only to a gravitational field. Synonyms: free fall.

(noun) a sudden sharp decrease in some quantity. Synonyms: drop, dip, fall, free fall. Examples: "A drop of 57 points on the dow jones index." "There was a drop in pressure in the pulmonary artery." "A dip in prices." "When that became known the price of their stock went into free fall."