free fall
     n 1: the ideal falling motion of something subject only to a
          gravitational field
     2: a sudden sharp decrease in some quantity; "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" [syn: {drop}, {dip}, {fall}]
Source: WordNet® 2.0