n.
Pronunciation: ō - ' i-d ē - ə m
Function: noun
Inflected Form: plural -ia \ -d ē - ə \
Etymology: New Latin, from o- + -idium
Date: 1857
1 a : any of a genus ( Oidium of the family Moniliaceae) of imperfect fungi many of which are now considered to be conidial stages of various powdery mildews b : one of the small conidia borne in chains by various fungi (as an oidium) ― called also arthrospore
2 : a powdery mildew especially of grapes caused by an oidium