The Collaborative International Dictionary of English v.0.48:

Precipitous \Pre*cip"i*tous\, a. [L. praeceps, -cipitis: cf. OF.
   precipiteux. See Precipice.]
   1. Steep, like a precipice; as, a precipitous cliff or
      mountain.
      [1913 Webster]

   2. Headlong; as, precipitous fall.
      [1913 Webster]

   3. Hasty; rash; quick; sudden; precipitate; as, precipitous
      attempts. --Sir T. Browne. "Marian's low, precipitous
      `Hush!'" --Mrs. Browning.
      [1913 Webster] -- Pre*cip"i*tous*ly, adv. --
      Pre*cip"i*tous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

precipitously
    adv 1: very suddenly and to a great degree; "conditions that
           precipitously increase the birthrate"; "prices rose
           sharply" [syn: precipitously, sharply]
    2: abruptly; in a precipitous manner; "the mountains rose
       precipitously from the shore"