Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
precipitous [prɪˈsɪpɪtəs] adj (steep) круто́й*крут , обры́вистый/обры́вист (hasty) поспе́шный*поспе́шен
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.