Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
perpendicular [pəːpənˈdɪkjulər] adj (line, surface) перпендикуля́рный*перпендикуля́рен (cliff, slope) отве́сный*отве́сен
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: