follow-up: A follow-up is an action or a thing, such as a second or subsequent visit, letter plan, etc, designed to be a further effort in achieving some goal. The word is also used as an adjective to mean"used or sent as a follow-up• follow-up:A follow-up is an action or a thing, such as a second or subsequent visit, letter, plan, etc., designed to be a further effort in achieving some goal. The word is also used as an adjective to mean "used or sent as a follow-up