HEBDOMAD Meaning of HEBDOMAD in English [heb.do.mad] n [L hebdomad-, hebdomas, fr. Gk, fr. hebdomos seventh, fr. hepta seven--more at seven] (1545) 1: a group of seven 2: a period of seven days: week Merriam-Webster English vocab. Английский словарь Merriam Webster. 2012