Definition of ergot
1
: the black or dark purple sclerotium of fungi (genus Claviceps) that occurs as a club-shaped body replacing the seed of a grass (such as rye);
also
: a fungus bearing ergots
2
: a disease of rye and other cereals caused by an ergot fungus
3 a
: the dried sclerotia of an ergot fungus grown on rye and containing several alkaloids (such as ergonovine and ergotamine)
b
: any of such alkaloids used medicinally for their contractile effect on smooth muscle (as of the uterus and or blood vessels)
