The Collaborative International Dictionary of English v.0.48:

Molasses \Mo*las"ses\, n. [F. m['e]lasse, cf. Sp. melaza, Pg.
   mela[,c]o, fr. L. mellaceus honeylike, honey-sweet, mel,
   mellis, honey. See Mellifluous, and cf. Melasses.]
   The thick, brown or dark colored, viscid, uncrystallizable
   sirup which drains from sugar, in the process of manufacture;
   any thick, viscid, sweet sirup made from vegetable juice or
   sap, as of the sorghum or maple. See Treacle.
   [1913 Webster]

WordNet (r) 3.0 (2006):

molasses
    n 1: thick dark syrup produced by boiling down juice from sugar
         cane; especially during sugar refining

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "molasses":
   adherent, adhesive, albumen, ambrosia, artificial sweetener,
   barnacle, batter, blackstrap, bonnyclabber, bramble, brier,
   bulldog, burr, butter, calcium cyclamate, cane syrup, cement,
   clabber, clover honey, comb honey, corn syrup, cornstarch, cream,
   curd, cyclamates, decal, decalcomania, dough, edulcoration,
   egg white, gaum, gel, gelatin, glair, glop, glue, gluten, goo,
   gook, goop, gruel, gumbo, gunk, honey, honeycomb, honeydew,
   honeypot, jam, jell, jelly, leech, limpet, loblolly, maple syrup,
   mucilage, mucus, nectar, pap, paste, plaster, porridge, prickle,
   pudding, pulp, puree, putty, remora, rob, saccharification,
   saccharin, semifluid, semiliquid, size, sodium cyclamate, sorghum,
   soup, starch, sticker, sticky mess, sugar, sugar-making,
   sugaring off, sweetener, sweetening, sweets, syrup, thorn,
   treacle