na-adjective, noun
mediocre and small-minded; of little talent and petty
A literary, somewhat archaic term describing a person of limited ability and narrow character. Not used in everyday speech.
彼は凡小な人物だが、妙に自信家だ。
He is a mediocre and petty person, yet strangely self-confident.
凡小の才に甘んじてはいけない。
You must not be content with mediocre talent.