The Collaborative International Dictionary of English v.0.48:

Overripe \O"ver*ripe"\, a.
   Matured to excess. --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

overripe
    adj 1: too ripe and beginning to turn soft

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "overripe":
   bad, barfy, brackish, cloying, fetid, foul, fulsome, high, icky,
   maggoty, mawkish, nasty, nauseant, nauseating, nauseous, noisome,
   noxious, offensive, over the hill, overblown, poisonous, rancid,
   rank, rebarbative, reign, rotten, rule, sickening, spoiled,
   stinking, sway, vile, vomity, weevily, yucky