IPA: /sɪnˈsɪrər/
KK: /sɪnˈsɪrər/
More genuine or honest than someone or something else.
She was more sincerer in her apology than he was in his.
Comparative: sincerer
Superlative: sincerest
Sincerer → It is formed from "sincere" (from Latin *sincerus*, meaning pure or clean) and "-er" (meaning a person who). The word "sincerer" refers to a person who is more pure or genuine in their intentions or feelings.
Think of someone who is 'pure' ('sincerus') in their feelings — that's why a 'sincerer' is someone who is more genuine.