The Collaborative International Dictionary of English v.0.48:

Laconic \La*con"ic\, Laconical \La*con"ic*al\, a. [L. Laconicus
   Laconian, Gr. ??, fr. ?? a Laconian, Laced[ae]monian, or
   Spartan: cf. F. laconique.]
   1. Expressing much in few words, after the manner of the
      Laconians or Spartans; brief and pithy; concise; brusque;
      epigrammatic. In this sense laconic is the usual form.
      [1913 Webster]

            I grow laconic even beyond laconicism; for sometimes
            I return only yes, or no, to questionary or
            petitionary epistles of half a yard long. --Pope.
      [1913 Webster]

            His sense was strong and his style laconic.
                                                  --Welwood.
      [1913 Webster]

   2. Laconian; characteristic of, or like, the Spartans; hence,
      stern or severe; cruel; unflinching.
      [1913 Webster]

            His head had now felt the razor, his back the rod;
            all that laconical discipline pleased him well.
                                                  --Bp. Hall.

   Syn: Short; brief; concise; succinct; sententious; pointed;
        pithy.

   Usage: Laconic, Concise. Concise means without irrelevant
          or superfluous matter; it is the opposite of diffuse.
          Laconic means concise with the additional quality of
          pithiness, sometimes of brusqueness.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Laconic \La*con"ic\, n.
   Laconism. [Obs.] --Addison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

laconic
    adj 1: brief and to the point; effectively cut short; "a crisp
           retort"; "a response so curt as to be almost rude"; "the
           laconic reply; `yes'"; "short and terse and easy to
           understand" [syn: crisp, curt, laconic, terse]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "laconic":
   Spartan, abbreviated, abridged, aposiopestic, brief, brusque,
   clipped, close, close-tongued, closemouthed, compact, compendious,
   compressed, concise, condensed, contracted, crisp, curt, cut,
   docked, dumb, economical of words, elliptic, epigrammatic, gnomic,
   indisposed to talk, mum, mute, pithy, pointed, pruned, quiet,
   reserved, sententious, short, short and sweet, shortened, silent,
   snug, sparing of words, speechless, succinct, summary, synopsized,
   taciturn, terse, tight, tight-lipped, to the point, tongue-tied,
   truncated, unloquacious, untalkative, word-bound, wordless