Adjective
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.
Disappointing; imperfect; unsound.
Source: Webster's dictionaryWell, youth is the period of assumed personalities and disguises. It is the time of the sincerely insincere. V. S. Pritchett
The most exhausting thing in life is being insincere. Anne Morrow Lindbergh
If we are not stupid or insincere when we say that the good or ill of man lies within his own will, and that all beside is nothing to us, why are we still troubled? Epictetus
Better an honest slap in the face than an insincere kiss. Yiddish Proverb
A hundred "no's" are less painful than one insincere "yes." Chinese Proverb
To act sincerely with the insincere is dangerous. Tao Proverb