/ ˌriːəˈʃʊə(r); -ʃɔː(r); NAmE -ˈʃʊr/ verb
reassure sb (about sth) to say or do sth that makes sb less frightened or worried
SYN set sb's mind at rest :
[ vn ]
They tried to reassure her, but she still felt anxious.
[ vn that ]
The doctor reassured him that there was nothing seriously wrong.