The Collaborative International Dictionary of English v.0.48:

Overflow \O`ver*flow"\, v. t. [imp. & p. p. Overflowed; p. pr.
   & vb. n. Overflowing.] [AS. oferfl?wan. See Over, and
   Flow.]
   1. To flow over; to cover woth, or as with, water or other
      fluid; to spread over; to inundate; to overwhelm.
      [1913 Webster]

            The northern nations overflowed all Christendom.
                                                  --Spenser.
      [1913 Webster]

   2. To flow over the brim of; to fill more than full.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Overflowing \O`ver*flow"ing\, n.
   An overflow; that which overflows; exuberance; copiousness.
   [1913 Webster]

         He was ready to bestow the overflowings of his full
         mind on anybody who would start a subject. --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overflowing
    adj 1: covered with water; "the main deck was afloat (or
           awash)"; "the monsoon left the whole place awash"; "a
           flooded bathroom"; "inundated farmlands"; "an overflowing
           tub" [syn: afloat(p), awash(p), flooded,
           inundated, overflowing]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "overflowing":
   abounding, abundant, affluent, alive with, all-sufficing, ample,
   aplenty, bloated, bottomless, bounteous, bountiful, bristling,
   bursting, choked, congested, copious, countless, crammed, crawling,
   crowded, crowding, diffuse, diffusive, distended, drenched, effuse,
   effusive, epidemic, exhaustless, extravagant, exuberant, fat,
   fecund, fertile, filled to overflowing, flush, formless, full,
   galore, generous, glutted, gorged, gushing, gushy, hyperemic,
   in plenty, in profusion, in quantity, in spate, inexhaustible,
   jam-packed, jammed, lavish, liberal, luxuriant, many, maximal,
   much, multitudinous, numerous, opulent, overabundant, overblown,
   overburdened, overcharged, overfed, overfraught, overfreighted,
   overfull, overladen, overloaded, overstocked, overstuffed,
   oversupplied, overweighted, packed, plenitudinous, plenteous,
   plentiful, plenty, pleonastic, plethoric, populous, prevailing,
   prevalent, prodigal, productive, profuse, profusive, proliferating,
   prolific, rampant, ready to burst, redundant, reiterative,
   repetitive, replete, rich, rife, riotous, running over, satiated,
   saturated, stuffed, stuffed up, superabundant, supercharged,
   supersaturated, surcharged, surfeited, swarming, swollen,
   tautologous, teeming, thick, thick as hail, thick with,
   thick-coming, thronged, thronging, wealthy, well-found,
   well-furnished, well-provided, well-stocked, wholesale