/ sɪnˈsɪə(r); NAmE -ˈsɪr/ adjective ( superlative sin·cerest , no comparative )
1.
( of feelings, beliefs or behaviour ) showing what you really think or feel
SYN genuine :
a sincere attempt to resolve the problem
sincere regret
Please accept our sincere thanks.
a sincere apology
2.
sincere (in sth) ( of a person ) saying only what you really think or feel
SYN honest :
He seemed sincere enough when he said he wanted to help.
She is never completely sincere in what she says about people.
OPP insincere
► sin·cer·ity / sɪnˈserəti; NAmE / noun [ U ]:
She spoke with total sincerity.
I can say in all sincerity that I knew nothing of these plans.
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WORD ORIGIN
mid 16th cent. (also in the sense not falsified, unadulterated ): from Latin sincerus clean, pure.