The Collaborative International Dictionary of English v.0.48:

Sketchy \Sketch"y\, a.
   Containing only an outline or rough form; being in the manner
   of a sketch; incomplete.
   [1913 Webster]

         The execution is sketchy throughout; the head, in
         particular, is left in the rough.        --J. S.
                                                  Harford.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sketchy
    adj 1: giving only major points; lacking completeness; "a
           sketchy account"; "details of the plan remain sketchy"
           [syn: sketchy, unelaborated]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "sketchy":
   adulterated, arrested, blemished, callow, crude, cursory, damaged,
   defective, deficient, depthless, embryonic, erroneous, failing,
   fallible, faulty, found wanting, fuzzy, hasty, hurried,
   hypoplastic, ill-defined, immature, impaired, imperfect, imprecise,
   impure, in arrear, in arrears, in default, in short supply,
   inaccurate, inadequate, incomplete, indistinct, inexact, infant,
   lacking, makeshift, mediocre, missing, mixed, needing, not perfect,
   off, part, partial, patchy, perfunctory, rough, rough-hewn, scant,
   scanty, scrappy, shallow, short, shy, skimpy, superficial,
   uncritical, underdeveloped, undeveloped, uneven, unfinished,
   unperfected, unpolished, unrefined, unsound, unthorough, vague,
   wanting