Longman Dictionary of Contemporary English
Wiktionary
n. Something used as a leverage in negotiations.
WordNet
n. leverage in the form of an inducement or a concession useful in successful negotiations
Usage examples of "bargaining chip".
The Republic's permanent renunciation of all claims to San Martin was simply too valuable a bargaining chip to give up until she got at least something in return.
The fact that his sister was the bargaining chip bothered them not at all.
But it was a bargaining chip to top all bargaining chips, the ace in the hole, the guaranteed result-getter.
On the other hand, having her body made for a potentially useful bargaining chip, and he was fairly sure that the little Bushman was with her, too, which might be an even greater pull on her loyalties than her own physical safety.
I escaped from that only to be driven over here and told my own death is the sole bargaining chip against the lives of eighty-eight more people.