The Collaborative International Dictionary of English v.0.48:

Rumple \Rum"ple\, v. t. & i. [imp. & p. p. Rumpled p. pr. &
   vb. n. Rumpling.] [Cf. rimple, and D. rimpelen to wrinkle,
   rompelig rough, uneven, G. r["u]mpfen to wrinkle, MHG.
   r["u]mphen, OHG. rimpfan, Gr. "ra`mfos the crooked beak of
   birds of prey, ? to roam.]
   To make uneven; to form into irregular inequalities; to
   wrinkle; to crumple; as, to rumple an apron or a cravat.
   [1913 Webster]

         They would not give a dog's ear of their most rumpled
         and ragged Scotch paper for twenty of your fairest
         assignats.                               --Burke.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rumple \Rum"ple\, n.
   A fold or plait; a wrinkle. --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rumple
    v 1: disturb the smoothness of; "ruffle the surface of the
         water" [syn: ruffle, ruffle up, rumple, mess up]
    2: to gather something into small wrinkles or folds; "She
       puckered her lips" [syn: pucker, rumple, cockle,
       crumple, knit]
    3: become wrinkled or crumpled or creased; "This fabric won't
       wrinkle" [syn: rumple, crumple, wrinkle, crease,
       crinkle]