I suppose it all comes down to whichever dictionary you subscribe to.

Aside from it not fitting on the board, it'd make a decent score in Scrabble:

  • Stab (6)
  • Establish (14)
  • Disestablishment (24+50=74)
  • Disestablishmentarian (29)
  • Antidisestablishmentarianism (38+50=88)

And by that time it would almost certainly be crossing at least two double word scores or three triple word scores. 38x2x2+50=202, 38x3x3x3+50=1076. Pitty the highest scoring letter is H (4).