The Collaborative International Dictionary of English v.0.48:

doodle \doo"dle\, n. [Cf. Dawdle.]
   A trifler; a simple fellow.
   [1913 Webster]

WordNet (r) 3.0 (2006):

doodle
    n 1: an aimless drawing [syn: scribble, scrabble, doodle]
    v 1: make a doodle; draw aimlessly

Moby Thesaurus II by Grady Ward, 1.0:

139 Moby Thesaurus words for "doodle":
   ass, bagpipe, beat, beguile the time, bilk, black and white, blow,
   blow a horn, born fool, brouillon, buffoon, bugle, burn daylight,
   carillon, cartoon, chalk, charcoal, charcoal drawing, cheat,
   chiaroscuro, chisel, clarion, clown, color, consume time, copy,
   cozen, crayon, crosshatch, dabble, dally, dash off, daub, dawdle,
   defraud, delineate, delineation, depict, design, diagram, diddle,
   dillydally, do, donkey, double-tongue, draft, draw, drawing,
   ebauche, egregious ass, esquisse, fife, figure of fun, flimflam,
   flute, fool, footle, fribble, fritter away time, graph, gyp, hatch,
   idiot, ignoramus, imbecile, jackass, jerk, kill time, lag, limn,
   line drawing, linger, lip, loiter, lollygag, lose time, lunatic,
   mess, mess around, milksop, mooncalf, nincompoop, ninny, overreach,
   paint, paint a picture, pass the time, pastel, pen-and-ink, pencil,
   pencil drawing, perfect fool, picture, picturize, piddle, pipe,
   poke, portray, potter, puddle, putter, rough copy, rough draft,
   rough outline, schmuck, scrabble, scratch, scrawl, scribble,
   scumble, shade, silhouette, silver-print drawing, sinopia, sketch,
   softhead, sop, sound, stencil, study, stupid ass, tinker, tint,
   tomfool, tongue, toot, tootle, trace, tracing, trifle,
   triple-tongue, trumpet, tweedle, vignette, waste time, whistle,
   wind, wind the horn, zany