difficult problem; tough person; hard nut to crack
Refers to a problem, task, or person that is difficult to handle or satisfy. Often used in business or personal contexts.
この交渉は難物だ。
This negotiation is a tough one.
彼はなかなかの難物で、誰も扱いきれない。
He is quite a difficult person; no one can handle him.
Compound of 難 (difficult) and 物 (thing/person). The exact historical derivation is uncertain, but the meaning follows directly from the kanji.