unplumbed(s = adj.all) profound, unfathomed, unsounded - situated at or extending to great depth; too deep to have been sounded or plumbed; "the profound depths of the sea"; "the dark unfathomed caves of ocean"; "unplumbed depths of the sea"; "remote and unsounded caverns"

unplumbed, adj.
1 not plumbed.
2 not fully explored or understood.

Derivative:
unplumbable adj.

N  size, magnitude, dimension, bulk, volume, largeness, greatness, expanse, amplitude, mass, proportions, capacity, tonnage, tunnage, cordage, caliber, scantling, turgidity, corpulence, obesity, plumpness, embonpoint, corporation, flesh and blood, lustihood, hugeness, enormity, immensity, monstrosity, giant, Brobdingnagian, Antaeus, Goliath, Gog and Magog, Gargantua, monster, mammoth, Cyclops, cachalot, whale, porpoise, behemoth, leviathan, elephant, hippopotamus, colossus, tun, cord, lump, bulk, block, loaf, mass, swad, clod, nugget, bushel, thumper, whooper, spanker, strapper, Triton among the minnows, mountain, mound, heap, largest portion, full size, life size, large, big, great, considerable, bulky, voluminous, ample, massive, massy, capacious, comprehensive, spacious, mighty, towering, fine, magnificent, corpulent, stout, fat, obese, plump, squab, full, lusty, strapping, bouncing, portly, burly, well-fed, full-grown, corn fed, gram fed, stalwart, brawny, fleshy, goodly, in good case, in good condition, in condition, chopping, jolly, chub faced, chubby faced, lubberly, hulky, unwieldy, lumpish, gaunt, spanking, whacking, whopping, walloping, thumping, thundering, hulking, overgrown, puffy, huge, immense, enormous, mighty, vast, vasty, amplitudinous, stupendous, monster, monstrous, humongous, monumental, elephantine, jumbo, mammoth, gigantic, gigantean, giant, giant like, titanic, prodigious, colossal, Cyclopean, Brobdingnagian, Bunyanesque, Herculean, Gargantuan, infinite, large as life, plump as a dumpling, plump as a partridge, fat as a pig, fat as a quail, fat as butter, fat as brawn, fat as bacon, immeasurable, unfathomable, unplumbed, inconceivable, unimaginable, unheard-of, of cosmic proportions, of epic proportions, the mother of all, teh granddaddy of all.