WordNet (r) 3.0 (2006):

pointlessness
    n 1: total lack of meaning or ideas [syn: inanity,
         senselessness, mindlessness, vacuity,
         pointlessness]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "pointlessness":
   absurdity, aimlessness, aridity, barrenness, bloodlessness,
   bootlessness, characterlessness, colorlessness, deadness,
   dismalness, dragginess, dreariness, dryness, dullness, dustiness,
   effeteness, emptiness, etiolation, fatuity, fecklessness, flatness,
   fruitlessness, futility, heaviness, hollowness, impotence, inanity,
   ineffectiveness, ineffectuality, inefficacy, inexcitability,
   insipidity, insipidness, jejunity, leadenness, lifelessness,
   lowness of spirit, meaninglessness, nugacity, otiosity, paleness,
   pallor, pokiness, ponderousness, profitlessness, purposelessness,
   rat race, slowness, solemnity, spiritlessness, sterility,
   stiffness, stodginess, stuffiness, superficiality, tastelessness,
   tediousness, the absurd, triviality, uninterestingness,
   unliveliness, unproductiveness, unprofitability, unprofitableness,
   valuelessness, vanity, vapidity, vapidness, vicious circle,
   woodenness, worthlessness