i-adjective
unusual; serious; extraordinary
Describes a situation, atmosphere, or feeling that is not ordinary, often implying something serious or alarming is happening. Commonly used in the phrase ただならない雰囲気 (a tense/unusual atmosphere).
See also: 只ならぬ
会議室にはただならない雰囲気が漂っていた。
There was an unusual tension in the air in the meeting room.
彼のただならない様子
i-adjective
Rare literary use meaning something is beyond comparison, often in a positive sense. More commonly expressed with 比類のない or 無類の in modern Japanese.
彼のただならない才能は、周囲の誰もが認めるところだった。
His incomparable talent was acknowledged by everyone around him.
His serious demeanor made me worry that something had happened.