The Collaborative International Dictionary of English v.0.48:

Residue \Res"i*due\ (r?z"?-d?), n. [F. r['e]sidu, L. residuum,
   fr. residuus that is left behind, remaining, fr. residere to
   remain behind. See Reside, and cf. Residuum.]
   1. That which remains after a part is taken, separated,
      removed, or designated; remnant; remainder.
      [1913 Webster]

            The residue of them will I deliver to the sword.
                                                  --Jer. xv. 9.
      [1913 Webster]

            If church power had then prevailed over its victims,
            not a residue of English liberty would have been
            saved.                                --I. Taylor.
      [1913 Webster]

   2. (Law) That part of a testeator's estate wwhich is not
      disposed of in his will by particular and special legacies
      and devises, and which remains after payment of debts and
      legacies.
      [1913 Webster]

   3. (Chem.) That which remains of a molecule after the removal
      of a portion of its constituents; hence, an atom or group
      regarded as a portion of a molecule; a moiety or
      group; -- used as nearly equivalent to radical, but in
      a more general sense.
      [1913 Webster +PJC]

   Note: The term radical is sometimes restricted to groups
         containing carbon, the term residue and moiety being
         applied to the others.
         [1913 Webster]

   4. (Theory of Numbers) Any positive or negative number that
      differs from a given number by a multiple of a given
      modulus; thus, if 7 is the modulus, and 9 the given
      number, the numbers -5, 2, 16, 23, etc., are residues.
      [1913 Webster]

   Syn: Rest; remainder; remnant; balance; residuum; remains;
        leavings; relics.
        [1913 Webster]

WordNet (r) 3.0 (2006):

residue
    n 1: matter that remains after something has been removed
    2: something left after other parts have been taken away; "there
       was no remainder"; "he threw away the rest"; "he took what he
       wanted and I got the balance" [syn: remainder, balance,
       residual, residue, residuum, rest]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "residue":
   afterglow, afterimage, balance, butt, butt end, candle ends, chaff,
   debris, detritus, dregs, end, excess, fag end, filings, fossil,
   heel, holdover, husks, leavings, leftover, leftovers,
   odds and ends, offscourings, orts, parings, rags, refuse, relics,
   remainder, remains, remnant, residual, residuum, rest, roach,
   rubbish, ruins, rump, sawdust, scourings, scraps, shadow, shavings,
   straw, stubble, stump, surplus, survival, sweepings, trace,
   vestige, waste



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

RESIDUE. That which remains of something after taking away a part of it; as,
the residue of an estate, which is what has not been particularly devised by
will.
     2. A will bequeathing the general residue of personal property, passes
to the residuary legatee everything not otherwise effectually disposed of
and it makes no difference whether a legacy falls into the estate by lapse,
or as void at law, the next of kin is equally excluded. 15 Ves. 416; 2 Mer.
392. Vide 7 Ves. 391; 4 Bro. C. C. 55; 1 Bro. C. C. 589; Rop. on Leg. Index,
h.t.; Worth. on Wills, 454.