The Collaborative International Dictionary of English v.0.48:

Pachak \Pa*chak"\, n. (Bot.)
   The fragrant roots of the Saussurea Costus, exported from
   India to China, and used for burning as incense. It is
   supposed to be the costus of the ancients. [Written also
   putchuck.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

costusroot \costusroot\ n.
   an annual herb (Saussurea costus) of the eastern Himalayas
   (Kashmir) having purple florets and a fragrant root that
   yields a volatile oil used in perfumery and for preserving
   furs.

   Syn: Saussurea costus, Saussurea lappa.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Saussurea costus
    n 1: annual herb of the eastern Himalayas (Kashmir) having
         purple florets and a fragrant root that yields a volatile
         oil used in perfumery and for preserving furs [syn:
         costusroot, Saussurea costus, Saussurea lappa]