The Collaborative International Dictionary of English v.0.48:

Petty \Pet"ty\ (p[e^]t"t[y^]), a. [Compar. Pettier
   (p[e^]t"t[i^]*[~e]r); superl. Pettiest.] [OE. petit, F.
   petit; probably of Celtic origin, and akin to E. piece. Cf.
   Petit.]
   Little; trifling; inconsiderable; unimportant; also,
   inferior; subordinate; as, a petty fault; petty complaints; a
   petty prince. --Denham.
   [1913 Webster]

         Like a petty god
         I walked about, admired of all.          --Milton.
   [1913 Webster]

   Petty averages. See under Average.

   Petty cash, money expended or received in small items or
      amounts.

   Petty officer, a subofficer in the navy, as a gunner, etc.,
      corresponding to a noncommissionned officer in the army.
      [1913 Webster]

   Note: For petty constable, petty jury, petty larceny, petty
         treason, See Petit.
         [1913 Webster]

   Syn: Little; diminutive; inconsiderable; inferior; trifling;
        trivial; unimportant; frivolous.
        [1913 Webster]

WordNet (r) 3.0 (2006):

petty
    adj 1: inferior in rank or status; "the junior faculty"; "a
           lowly corporal"; "petty officialdom"; "a subordinate
           functionary" [syn: junior-grade, lower-ranking,
           lowly, petty(a), secondary, subaltern]
    2: (informal) small and of little importance; "a fiddling sum of
       money"; "a footling gesture"; "our worries are lilliputian
       compared with those of countries that are at war"; "a little
       (or small) matter"; "a dispute over niggling details";
       "limited to petty enterprises"; "piffling efforts"; "giving a
       police officer a free meal may be against the law, but it
       seems to be a picayune infraction" [syn: fiddling,
       footling, lilliputian, little, niggling, piddling,
       piffling, petty, picayune, trivial]
    3: contemptibly narrow in outlook; "petty little comments";
       "disgusted with their small-minded pettiness" [syn: petty,
       small-minded]
    n 1: larceny of property having a value less than some amount
         (the amount varies by locale) [syn: petit larceny, petty
         larceny, petty] [ant: grand larceny, grand theft]

Moby Thesaurus II by Grady Ward, 1.0:

176 Moby Thesaurus words for "petty":
   Mickey Mouse, abject, abominable, arrant, atrocious, authoritarian,
   base, beggarly, bickering, bigot, bigoted, borne, captious, casual,
   caviling, cheap, cheesy, choplogic, close, closed, constricted,
   contemptible, cramped, creedbound, crummy, cursory, deaf,
   deaf to reason, debased, deficient, degraded, depraved, depthless,
   despicable, dinky, dirty, disgusting, equivocatory, evasive,
   execrable, fanatical, few, flagrant, footling, foul, fulsome,
   grave, gross, grudging, hairsplitting, hedging, heinous, hidebound,
   illiberal, imperfect, impertinent, inadequate, incompetent,
   inconsequent, inconsequential, inconsiderable, inessential,
   inferior, insignificant, insufficient, insular, irrelevant,
   jerkwater, light, little, little-minded, logic-chopping, low,
   low-down, lumpen, maladroit, mangy, meager, mean, mean-minded,
   mean-spirited, measly, mediocre, mingy, miniature, minor,
   miserable, miserly, monstrous, narrow, narrow-hearted,
   narrow-minded, narrow-souled, narrow-spirited, nearsighted,
   nefarious, negligible, niggardly, niggling, nit-picking,
   no great shakes, not comparable, not in it, nugatory, obnoxious,
   odious, of no account, one-horse, out of it, paltering, paltry,
   parochial, parsimonious, peanut, peddling, pettifogging, picayune,
   picayunish, piddling, piffling, pimping, poky, poor, provincial,
   punk, puny, purblind, pussyfooting, quibbling, rank, reptilian,
   scabby, scrubby, scruffy, scummy, scurvy, shabby, shallow, shoddy,
   shoestring, short, shortsighted, shuffling, skin-deep, slight,
   small, small-beer, small-minded, small-time, squalid, stingy,
   straitlaced, stuffy, superficial, tight, tight-fisted, tinhorn,
   tiny, trichoschistic, trifling, trinal, trivial, two-bit,
   two-by-four, twopenny-halfpenny, uncatholic, uncharitable,
   unchivalrous, unconsidered, ungenerous, unimportant, unliberal,
   unmentionable, unskillful, vile, wretched