Main Entry: oid·i·um

Pronunciation: \ō-ˈi-dē-əm\

Function: noun

Inflected Form(s): plural -ia\-dē-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