na-adjective, noun which may take the genitive case particle 'no', noun
unfaithful; insincere; perfidious
Describes a person, action, or attitude lacking sincerity, loyalty, or truthfulness. Often used in formal or literary contexts to criticize betrayal or dishonesty.
I was disappointed by his insincere attitude.
He was accused of perfidy.
不実 describes someone who is unfaithful or insincere, the direct opposite of being 誠実.
false entry in an officially authenticated document
Compound of 不 (fu, 'not') and 実 (jitsu, 'truth, sincerity'). The kanji combination directly conveys the meaning of lacking truthfulness or fidelity.