adjective
insincere
in-sin-SEER/ˌɪnsɪnˈsɪr/
Not expressing genuine feelings, beliefs, or intentions.
The woman's congratulations are insincere, contradicted by her hidden thumbs-down gesture.

Etymology
Sincerus described things as pure or unmixed and, figuratively, people as genuine or truthful. Adding “not” gives the idea of feelings or statements adulterated by pretense rather than honestly expressed.
In context
Empty flattery or overly exaggerated praise can often come across as insincere,
More examples
- She recognized the insincere praise immediately.
- He gave an insincere promise merely to end the argument.
- Their friendly manner concealed an insincere offer of help.
Forms
insincere · more insincere · most insincere
insincerity noun — a lack of genuine feeling or belief
Similar words
- false
- False broadly means untrue; insincere specifically means not expressing one’s real feelings or beliefs.
- hypocritical
- Hypocritical involves a gap between professed values and behavior; insincere can concern any untruthful expression of feeling.