noun

• The act or quality of endorsing
• An amendment or annotation to an insurance contract or other official document (such as a driving licence).
• (aviation) An instructor's signed acknowledgement of time practising specific flying skills.
• (education, certification) Permission to carry out a specific skill or application in a field in which the practitioner already has a general licence.
• Sponsorship, in means of money, by a company, business or enterprise.
• Support from an important, renowned figure of a media (celebrity, politics, sports, etc.), to get back up.