INFIRM Meaning of INFIRM in English adj.1 physically weak, esp. through age. 2 (of a person, mind, judgement, etc.) weak, irresolute. Derivatives: infirmity n. (pl. -ies). infirmly adv. Etymology: ME f. L infirmus (as IN-(1), FIRM(1)) Oxford English vocab. Оксфордский английский словарь. 2012