na-adjective
Describes a feeling of pride or triumph, often with a sense of openness or expansiveness. Less common than 誇らしい (ほこらしい) in modern Japanese.
彼は誇らかな気持ちで賞を受け取った。
He accepted the award with a proud feeling.
その知らせを聞いて、彼女は誇らかに微笑んだ。
Hearing the news, she smiled proudly.
誇らしい is the more common modern adjective for 'proud'. 誇らか is less frequent and has a slightly more literary or expansive nuance.
Derived from the stem 誇 (ほこ) of the verb 誇る (ほこる, 'to be proud') plus the adjectival suffix らか, which forms adjectives expressing a state or quality. The exact historical development is uncertain.