The Collaborative International Dictionary of English v.0.48:

Succulent \Suc"cu*lent\, a. [L. succulentus, suculentus, fr.
   succus, sucus, juice; perhaps akin to E. suck: cf. F.
   succulent.]
   Full of juice; juicy.
   [1913 Webster]

   Succulent plants (Bot.), plants which have soft and juicy
      leaves or stems, as the houseleek, the live forever, and
      the species of Mesembryanthemum.
      [1913 Webster]

WordNet (r) 3.0 (2006):

succulent
    adj 1: full of juice; "lush fruits"; "succulent roast beef";
           "succulent plants with thick fleshy leaves" [syn: lush,
           succulent]
    n 1: a plant adapted to arid conditions and characterized by
         fleshy water-storing tissues that act as water reservoirs

Moby Thesaurus II by Grady Ward, 1.0:

142 Moby Thesaurus words for "succulent":
   agreeable, algae, ambrosial, autophyte, baccate, bean, bracken,
   brown algae, climber, comestible, conferva, confervoid, creeper,
   dainty, delectable, delicate, delicious, delightful, diatom,
   doughy, eatable, edible, esculent, exciting, exquisite, fern,
   flabby, flavorsome, fleshy, flowing, fluent, fluid, fluidal,
   fluidic, fluxible, fluxile, fluxional, fluxionary,
   fruits and vegetables, fucus, fungus, good, good to eat,
   good-tasting, grapevine, green algae, gulfweed, gustable, gusty,
   herb, heterophyte, interesting, inviting, ivy, juicy, kelp, kosher,
   legume, lentil, liana, lichen, likable, liquid, liquidy, lively,
   liverwort, luscious, lush, macerated, masticated, mold, moss,
   mouth-watering, mushroom, mushy, nectareous, nectarous, nice,
   of gourmet quality, palatable, parasite, parasitic plant, pasty,
   pea, perthophyte, phytoplankton, piquant, pithy, planktonic algae,
   plant families, pleasing, provocative, provoking, puffball, pulpal,
   pulpar, pulped, pulplike, pulpy, pulse, racy, readable, red algae,
   rich, rockweed, runny, rust, sapid, sappy, saprophyte, sargasso,
   sargassum, savorous, savory, scrumptious, sea lentil, sea moss,
   sea wrack, seaweed, smut, soft, spicy, spongy, squashy, squelchy,
   squishy, stimulating, tantalizing, tasty, thought-challenging,
   thought-inspiring, thought-provoking, tickling, titillating,
   toadstool, toothsome, vetch, vine, watery, wort, wrack, yummy