cro·tox·in 
(krō′tŏksĭn)
(krō′tŏksĭn)n.
A crystalline neurotoxin found in the venom of the rattlesnake Crotalus durissus subsp. terrificus.
[New Latin Crotalus, rattlesnake genus (from Latin crotalum, kind of rattle or castanet, from Greek krotalon, clapper, from krotein, to strike, beat) + TOXIN.]