Definitions of negotiable
able to be negotiated (=discussed or changed in order to reach agreement)
The precise details are still negotiable.
where the title (=ownership) of a legal document is able to be transferred (=passed from one person or institution to another) or assigned (=where the associated rights and duties are passed from one person or institution to another)
Promissory notes and bills of exchange are the two main types of negotiable instruments.