The Collaborative International Dictionary of English v.0.48:

Inarticulate \In`ar*tic"u*late\, a. [L. inarticulatus; pref. in-
   not + articulatus articulate.]
   [1913 Webster]
   1. Not uttered with articulation or intelligible
      distinctness, as speech or words.
      [1913 Webster]

            Music which is inarticulate poesy.    --Dryden.
      [1913 Webster]

   2. (Zool.)
      (a) Not jointed or articulated; having no distinct body
          segments; as, an inarticulate worm.
      (b) Without a hinge; -- said of an order (Inarticulata
          or Ecardines) of brachiopods.
          [1913 Webster]

   3. Incapable of articulating. [R.]
      [1913 Webster]

            The poor earl, who is inarticulate with palsy.
                                                  --Walpole.

   4. Incapable of expressing one's ideas or feelings clearly.
      [PJC]

WordNet (r) 3.0 (2006):

inarticulate
    adj 1: without or deprived of the use of speech or words;
           "inarticulate beasts"; "remained stupidly inarticulate
           and saying something noncommittal"; "inarticulate with
           rage"; "an inarticulate cry" [syn: inarticulate,
           unarticulate] [ant: articulate]