The Collaborative International Dictionary of English v.0.48:

Derivative \De*riv"a*tive\, a. [L. derivativus: cf. F.
   d['e]rivatif.]
   Obtained by derivation; derived; not radical, original, or
   fundamental; originating, deduced, or formed from something
   else; secondary; as, a derivative conveyance; a derivative
   word.
   [1913 Webster]

   2. Hence, unoriginal (said of art or other intellectual
      products.
      [PJC]

   Derivative circulation, a modification of the circulation
      found in some parts of the body, in which the arteries
      empty directly into the veins without the interposition of
      capillaries. --Flint. -- De*riv"a*tive*ly, adv. --
      De*riv"a*tive*ness, n.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Derivative \De*riv"a*tive\, n.
   1. That which is derived; anything obtained or deduced from
      another.
      [1913 Webster]

   2. (Gram.) A word formed from another word, by a prefix or
      suffix, an internal modification, or some other change; a
      word which takes its origin from a root.
      [1913 Webster]

   3. (Mus.) A chord, not fundamental, but obtained from another
      by inversion; or, vice versa, a ground tone or root
      implied in its harmonics in an actual chord.
      [1913 Webster]

   4. (Med.) An agent which is adapted to produce a derivation
      (in the medical sense).
      [1913 Webster]

   5. (Math.) A derived function; a function obtained from a
      given function by a certain algebraic process.
      [1913 Webster]

   Note: Except in the mode of derivation the derivative is the
         same as the differential coefficient. See Differential
         coefficient, under Differential.
         [1913 Webster]

   6. (Chem.) A substance so related to another substance by
      modification or partial substitution as to be regarded as
      derived from it; thus, the amido compounds are derivatives
      of ammonia, and the hydrocarbons are derivatives of
      methane, benzene, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

derivative
    adj 1: resulting from or employing derivation; "a derivative
           process"; "a highly derivative prose style"
    n 1: the result of mathematical differentiation; the
         instantaneous change of one quantity relative to another;
         df(x)/dx [syn: derived function, derivative,
         differential coefficient, differential, first
         derivative]
    2: a compound obtained from, or regarded as derived from,
       another compound
    3: a financial instrument whose value is based on another
       security [syn: derivative instrument, derivative]
    4: (linguistics) a word that is derived from another word;
       "`electricity' is a derivative of `electric'"

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "derivative":
   accountable, acquired, alleged, ascribable, assignable,
   attributable, attributed, borrowed, by-product, charged, conjugate,
   consequent, consequential, copied, credited, derivable from,
   derivation, derivational, derived, descendant, development, due,
   echoic, ensuing, etymologic, explicable, final, following,
   imitative, imputable, imputed, lexical, lexicographic, lexicologic,
   lexigraphic, noncreative, nongerminal, nonseminal, obtained,
   offshoot, onomastic, onomatologic, onomatopoeic, owing, paronymic,
   paronymous, plagiarized, procured, putative, referable,
   referred to, resultant, resulting, sequacious, sequent, sequential,
   spin-off, traceable, uncreative, uninventive, unoriginal,
   unpregnant



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

DERIVATIVE. Coming from another; taken from something preceding, secondary;
as derivative title, which is that acquired from another person. There is
considerable difference between an original and a derivative title. When the
acquisition is original, the right thus acquired to the thing becomes
property, which must be unqualified and unlimited, and since no one but the
occupant has any right to the thing, he must have the whole right of
disposing of it. But with regard to derivative acquisition, it may be
otherwise, for the person from whom the thing is acquired may not have an
unlimited right to it, or he may convey or transfer it with certain
reservations of right. Derivative title must always be by contract.
     2. Derivative conveyances are, those which presuppose some other
precedent conveyance, and serve only to enlarge, confirm, alter, restrain,
restore, or transfer the interest granted by such original conveyance, 3 Bl.
Com. 321.