D defs.my
Entry 2 senses Webster, 1913

Insincere

/ĭnˌ-sĭn-sĭr'/ · In·sin·cere · IPA /ˌɪnsɪnsˈɪr/
01 a. Not being in truth what one appears to be; not sincere; dissembling; hypocritical; disingenuous; deceitful; false; -- said of persons; also…
  1. 1.
    Not being in truth what one appears to be; not sincere; dissembling; hypocritical; disingenuous; deceitful; false; -- said of persons; also of speech, thought; etc.; as, insincere declarations.
  2. 2.
    Disappointing; imperfect; unsound.[Obs.]
    “To render sleep's soft blessings insincere.” Pope.