as·sure/ə`ʃr; əˈʃʊə/ v [T] spoken to tell someone that something will definitely happen or is definitely true, so that they are less worried 【口】 使〔某人〕确信［放心］; 向〔某人〕保证: The document is genuine, I can assure you. 这份文件是真的，我可以向你保证。 assure sb (that) The doctor assured me that I wouldn't feel any pain. 医生向我保证，我不会感觉到任何疼痛。