brazen-faced; shameless; thick-skinned
Idiomatic expression describing someone who is utterly shameless or audacious, as if their heart were covered in hair. Often used in a critical or exasperated tone.
Telling a lie like that—what a brazen-faced guy.
She remained completely unruffled, as if she had no shame at all.
厚かましい is a common adjective for 'shameless' or 'impudent', while 心臓に毛が生えた is a more vivid, idiomatic phrase emphasizing audacity.
図々しい also means 'impudent' or 'shameless', but 心臓に毛が生えた carries a stronger image of brazenness and is more colloquial.
Standard kanji spelling for this idiomatic expression.
Mixed kanji-kana spelling; the kana け makes the reading clearer.
The phrase literally means 'hair has grown on one's heart', implying a heart so calloused or insensitive that it grows hair, hence a person is shameless or brazen. The exact origin is uncertain, but it is a well-established Japanese idiom.