monthly /ˈmʌnθli/noun 2adjective 1adverb 1forms 1 noun2 •A publication that is published once a month.Of the 10 monthlies with the worst declines in January, four were Condé Nast magazines: Wired, Architectural Digest, Vogue and Lucky. — 2009 •(informal, euphemistic) The menstrual period.Katherine assumed she was having her monthly. She could recall times when her own monthly was so intense that it showed on her face. — 2008 adjective1 •Occurring every month.It's time give the dog its monthly bath. adverb1 •Every month.Rent must be paid monthly. formsmonthlies