'crottal' definitions:

Definition of 'crottal'

(from WordNet)
noun
Any of several lichens of the genus Parmelia from which reddish brown or purple dyes are made [syn: crottle, crottal, crotal]

Definition of 'crottal'

From: GCIDE
  • crottal \crottal\ n. any of several lichens of the genus Parmelia from which reddish brown or purple dyes are made. [Also spelled crottle and crotal.]
  • Syn: . [WordNet 1.5]