crotal vs crottal

crotal and crottal both are nouns.

Word	Noun	Adjective	Verb	Adverb
crotal	Yes	No	No	No
crottal	Yes	No	No	No

As nouns, crotal and crottal are synonyms defined as:

crotal and crottal: any of several lichens of the genus Parmelia from which reddish brown or purple dyes are made

Other synonyms of crotal include crottle.

crotal (noun)	crottal (noun)
any of several lichens of the genus Parmelia from which reddish brown or purple dyes are made	any of several lichens of the genus Parmelia from which reddish brown or purple dyes are made