The Collaborative International Dictionary of English v.0.48:

blotto \blot"to\ adj. (bl[o^]t"t[-o])
   drunk[1]. [colloq.]
   [PJC]

WordNet (r) 3.0 (2006):

blotto
    adj 1: very drunk [syn: besotted, blind drunk, blotto,
           crocked, cockeyed, fuddled, loaded, pie-eyed,
           pissed, pixilated, plastered, slopped, sloshed,
           smashed, soaked, soused, sozzled, squiffy,
           stiff, tight, wet]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "blotto":
   blind, blind drunk, boozy, canned, disguised, drunk, helpless,
   inebriated, muddled, out, out cold, overcome, paralyzed,
   passed out, pixilated, plastered, stiff, stoned, under the table