The Collaborative International Dictionary of English v.0.48:

Transpicuous \Tran*spic"u*ous\, a. [L. transpicere to see or
   look through + specere, spicere, to see. Cf. Conspicuous.]
   Transparent; pervious to the sight. [R.] "The wide,
   transpicuous air." --Milton.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "transpicuous":
   clean-cut, clear, clear as crystal, clear as day, clear-cut,
   coherent, connected, consistent, crisp, crystal, crystal-clear,
   crystalline, defined, definite, diaphane, diaphanous, direct,
   distinct, explicit, express, filmy, gauzy, gossamer, gossamery,
   light-pervious, limpid, loud and clear, lucent, lucid, luminous,
   nonopaque, peekaboo, pellucid, perspicuous, plain, revealing,
   see-through, sheer, simple, straightforward, thin, translucent,
   transparent, unambiguous, unclouded, unconfused, unequivocal,
   univocal, unmistakable, well-defined