in ‧ sin ‧ cere /ˌɪnsɪnˈsɪə◂ $ -ˈsɪr◂/ BrE AmE adjective
pretending to be pleased, sympathetic etc, especially by saying nice things, but not really meaning what you say:
an insincere smile
an offer which she knew to be impractical and insincere
—insincerely adverb
—insincerity /ˌɪnsɪnˈserəti, ˌɪnsɪnˈserɪti/ noun [uncountable]