WordNet (r) 3.0 (2006):

last word
    n 1: the final statement in a verbal argument; "she always gets
         the last word"
    2: an authoritative statement; "my doctor has the last word on
       the medicines I take"
    3: elegance by virtue of being fashionable [syn: chic,
       chicness, chichi, modishness, smartness,
       stylishness, swank, last word]

Moby Thesaurus II by Grady Ward, 1.0:

126 Moby Thesaurus words for "last word":
   PS, Parthian shot, Z, acme, acme of perfection, addendum,
   advance guard, afterthought, apodosis, appendix, avant-garde,
   back matter, catastrophe, ceasing, cessation, chorus, climax, coda,
   codicil, colophon, conclusion, consequence, consummation,
   continuance, continuation, crack of doom, culmination, curtain,
   curtains, death, decease, denouement, destination, destiny, doom,
   double take, dying words, effect, end, end point, ending, envoi,
   epilogue, epitome, eschatology, expiration, fate, final offer,
   final solution, final twitch, final words, finale, finality, finis,
   finish, firm price, follow-through, follow-up, goal, height,
   highest pitch, innovation, izzard, last, last breath, last gasp,
   last things, last trumpet, last words, latest fad, latest fashion,
   latest wrinkle, latter end, ne plus ultra, new look,
   newfangled device, novelty, omega, parting shot, payoff, peak,
   perfection, period, peroration, pink, pink of perfection, pinnacle,
   postface, postfix, postlude, postscript, quietus, quintessence,
   refrain, resolution, resting place, second thought, sequel,
   sequela, sequelae, sequelant, sequent, sequitur, stoppage,
   stopping place, subscript, suffix, summit, supplement, swan song,
   tag, term, terminal, termination, terminus, the in thing,
   the last word, the latest thing, the latest wrinkle, the rage,
   the thing, top, ultimate, ultimatum, vanguard, windup