ˈhebdəˌmad noun
( -s )
Etymology: Latin hebdomad-, hebdomas, from Greek hebdomad-, hebdomas, from hebdomos seventh (from hepta seven) + -ad-, -as feminine suffix denoting connection with or descent from — more at seven
1. : a group of seven
a hebdomad of heavenly bodies
2. : a period of seven days : week
3. gnosticism : a group of seven aeons derived from the seven planetary deities who in most systems were half-hostile powers that created the world