The Collaborative International Dictionary of English v.0.48:

Captious \Cap"tious\, a. [F. captieux, L. captiosus. See
   Caption.]
   1. Apt to catch at faults; disposed to find fault or to
      cavil; eager to object; difficult to please.
      [1913 Webster]

            A captious and suspicious age.        --Stillingfleet.
      [1913 Webster]

            I am sensible I have not disposed my materials to
            abide the test of a captious controversy. --Bwike.
      [1913 Webster]

   2. Fitted to harass, perplex, or insnare; insidious;
      troublesome.
      [1913 Webster]

            Captious restraints on navigation.    --Bancroft.

   Syn: Caviling, carping, fault-finding; censorious;
        hypercritical; peevish, fretful; perverse; troublesome.

   Usage: Captious, caviling, Carping. A captious person
          is one who has a fault-finding habit or manner, or is
          disposed to catch at faults, errors, etc., with
          quarrelsome intent; a caviling person is disposed to
          raise objections on frivolous grounds; carping implies
          that one is given to ill-natured, persistent, or
          unreasonable fault-finding, or picking up of the words
          or actions of others.
          [1913 Webster]

                Caviling is the carping of argument, carping the
                caviling of ill temper.           --C. J. Smith.
          [1913 Webster]

WordNet (r) 3.0 (2006):

captious
    adj 1: tending to find and call attention to faults; "a captious
           pedant"; "an excessively demanding and faultfinding
           tutor" [syn: captious, faultfinding]

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "captious":
   bickering, carping, caviling, censorious, choplogic, contrary,
   critic, critical, cynical, demanding, equivocatory, evasive,
   exacting, faultfinding, finicky, hairsplitting, hedging,
   hypercritical, irritable, logic-chopping, nagging, niggling,
   nit-picking, overcritical, paltering, particular, peevish,
   pernickety, perverse, pettifogging, petty, petulant, picayune,
   pussyfooting, quibbling, shuffling, snappish, snappy, testy,
   trichoschistic, trifling, trivial, ultracritical