The Collaborative International Dictionary of English v.0.48:

Asceticism \As*cet"i*cism\, n.
   The condition, practice, or mode of life, of ascetics.
   [1913 Webster]

WordNet (r) 3.0 (2006):

asceticism
    n 1: the doctrine that through renunciation of worldly pleasures
         it is possible to achieve a high spiritual or intellectual
         state
    2: the trait of great self-denial (especially refraining from
       worldly pleasures) [syn: austerity, asceticism,
       nonindulgence]
    3: rigorous self-denial and active self-restraint [syn:
       asceticism, ascesis]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "asceticism":
   Day of Atonement, Encratism, Friday, Lenten fare, Pythagoreanism,
   Pythagorism, Rechabitism, Shakerism, Spartan fare, Stoicism,
   Yom Kippur, abstainment, abstemiousness, abstention, abstinence,
   avoidance, banyan day, celibacy, chastity, cold purgatorial fires,
   continence, eschewal, fast, fasting, fish day, flagellation,
   fruitarianism, gymnosophy, hair shirt, lustration, maceration,
   mortification, nephalism, penance, penitence, penitential act,
   penitential exercise, plain living, purgation, purgatory,
   refraining, refrainment, repentance, sackcloth and ashes,
   sexual abstinence, simple diet, spare diet, teetotalism,
   the pledge, total abstinence, vegetarianism