WordNet (r) 3.0 (2006):

out of bounds
    n 1: a line that marks the side boundary of a playing field
         [syn: sideline, out of bounds]

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "out of bounds":
   a bit much, abandoned, banned, barred, boundless, contraband,
   cutthroat, egregious, enormous, exacting, exaggerated, excessive,
   exorbitant, extortionate, extravagant, extreme, fabulous, fancy,
   forbade, forbid, forbidden, gigantic, gluttonous, gouging,
   grossly overpriced, high, hyperbolic, hypertrophied, illegal,
   illicit, immoderate, incontinent, inflationary, inordinate,
   intemperate, monstrous, nonpermissible, not permitted, off limits,
   out of sight, outlawed, outrageous, overbig, overdeveloped,
   overgreat, overgrown, overlarge, overmuch, overpriced, overweening,
   preposterous, prohibited, prohibitive, restricted, ruled out,
   skyrocketing, spiraling, steep, stiff, taboo, tabooed, too much,
   unallowed, unauthorized, unbridled, unconscionable, under the ban,
   undue, unlawful, unlicensed, unpermissible, unreasonable,
   unrestrained, unsanctioned, untouchable, unwarranted, usurious,
   verboten, vetoed