The Collaborative International Dictionary of English v.0.48:

Drivel \Driv"el\, v. i. [imp. & p. p. Driveledor Drivelled;
   p. pr. & vb. n. Driveling or Drivelling.] [Cf. OE.
   dravelen, drabelen, drevelen, drivelen, to slaver, and E.
   drabble. Cf. Drool.]
   1. To slaver; to let spittle drop or flow from the mouth,
      like a child, idiot, or dotard.
      [1913 Webster]

   2. [Perh. a different word: cf. Icel. drafa to talk thick.]
      To be weak or foolish; to dote; as, a driveling hero;
      driveling love. --Shak. Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Drivel \Driv"el\, n.
   1. Slaver; saliva flowing from the mouth.
      [1913 Webster]

   2. Inarticulate or unmeaning utterance; foolish talk; babble.
      [1913 Webster]

   3. A driveler; a fool; an idiot. [Obs.] --Sir P. Sidney.
      [1913 Webster]

   4. A servant; a drudge. [Obs.] --Huloet.
      [1913 Webster]

WordNet (r) 3.0 (2006):

drivel
    n 1: a worthless message [syn: drivel, garbage]
    2: saliva spilling from the mouth [syn: drool, dribble,
       drivel, slobber]
    v 1: let saliva drivel from the mouth; "The baby drooled" [syn:
         drivel, drool, slabber, slaver, slobber,
         dribble]

Moby Thesaurus II by Grady Ward, 1.0:

118 Moby Thesaurus words for "drivel":
   Greek, absurdity, amphigory, babble, babblement, balderdash, balls,
   baloney, be insane, be stupid, bibble-babble, blabber, blather,
   blatherskite, blither, blow, blunder away, bombast, bosh, bull,
   bullshit, burble, cast away, chatter, claptrap, consume, crap,
   dither, dote, double-talk, dribble, drool, expectorate,
   expectoration, eyewash, fiddle-faddle, fiddledeedee, flapdoodle,
   flummery, foam, folderol, fritter, froth, fudge, fustian, gab,
   gabble, galimatias, gammon, garbage, gas, gibber, gibberish,
   gibble-gabble, gobbledygook, have a demon, hawk, hocus-pocus,
   hogwash, hooey, hot air, humbug, jabber, jabberwocky, jargon,
   malarkey, maunder, mouth-watering, mumbo jumbo, narrishkeit,
   niaiserie, nonsense, pack of nonsense, palaver, piffle, prate,
   prattle, ptyalism, rage, ramble, rant, rattle, rave, rigamarole,
   rigmarole, rodomontade, rubbish, run amok, run mad, saliva,
   salivate, salivation, sialagogue, skimble-skamble, slabber, slaver,
   slobber, spew, spit, spittle, sputum, squander, stuff and nonsense,
   stultiloquence, talk nonsense, throw away, trash, trifle away,
   tripe, trumpery, twaddle, twattle, twiddle-twaddle, vapor,
   vaporing, waffle, waffling, wander