noun which may take the genitive case particle 'no'
Almost exclusively used in the compound 正真正銘 (しょうしんしょうめい), meaning 'genuine' or 'the real thing'. Rarely used independently in modern Japanese.
See also: 正真正銘
これは正真正銘のダイヤモンドだ。
This is a genuine diamond.
彼の話は正真正銘の真実だ。
His story is the absolute truth.
Composed of 正 (correct, true) and 真 (truth, reality). The exact historical derivation is uncertain; the combination reinforces the meaning of genuineness.