in flagrante
adverb uk/ˌɪn fləˈɡræn.teɪ/ us/ˌɪn fləˈɡræn.teɪ/ (also in flagrante delicto, /ɪn fləˌɡræn.teɪ dəˈlɪk.təʊ/ /ˌɪn fləˌɡræn.teɪ dəˈlɪk.toʊ/)
当场（尤指被捉奸）;在作案现场
in the act of doing something wrong, especially having sex with someone who is not your husband, wife, or usual partner
She returns home early to find her husband in flagrante delicto with a neighbour. 她提早回家，结果当场将丈夫和邻居捉奸在床。