The Collaborative International Dictionary of English v.0.48:

Negotiable \Ne*go"ti*a*ble\ (? or ?), a. [Cf. F. n['e]gotiable.
   See Negotiate.]
   Capable of being negotiated; transferable by assignment or
   indorsement to another person; as, a negotiable note or bill
   of exchange.
   [1913 Webster]

   Negotiable paper, any commercial paper transferable by sale
      or delivery and indorsement, as bills of exchange, drafts,
      checks, and promissory notes.
      [1913 Webster]

WordNet (r) 3.0 (2006):

negotiable
    adj 1: capable of being passed or negotiated; "a negotiable
           road"
    2: able to be negotiated or arranged by compromise; "negotiable
       demands"; "the proposal is still on the table" [syn:
       negotiable, on the table]
    3: legally transferable to the ownership of another; "negotiable
       bonds" [syn: assignable, conveyable, negotiable,
       transferable, transferrable]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "negotiable":
   achievable, actable, alienable, assignable, attainable,
   bequeathable, compassable, consignable, convertible, conveyable,
   devisable, doable, feasible, heritable, inheritable, liquid,
   manageable, maneuverable, manipulatable, operable, operatable,
   overcomable, performable, practicable, practical, realizable,
   superable, surmountable, transferable, viable, workable



Bouvier's Law Dictionary, Revised 6th Ed (1856):

NEGOTIABLE. That which is capable of being transferred by assignment; a
thing, the title to which may be transferred by a sale and indorsement or
delivery.
     2. A chose in action was not assignable at common law, and therefore
contracts or agreements could not be negotiated. But exceptions have been
allowed to this rule in relation to simple contracts, and others have been
introduced by legislative acts. So that, now, bills of exchange, promissory
notes, bills of lading, bank notes, payable to order, or to bearer, and, in
some states, bonds and other specialties, may be transferred by assignment,
indorsement, or by delivery, when the instrument is payable to bearer.
     3. When a claim is assigned which is not negotiable at law, such, for
example, as a book debt, the title to it remains at law in the assigner, but
the assignee is entitled to it in equity, and he may therefore recover it in
the assignor's name. See, generally, Hare & Wall. Sel. Dec. 158 to 194
Negotiable paper.