The Collaborative International Dictionary of English v.0.48:

Quietist \Qui"et*ist\, n. [Cf. F. qui['e]tiste.] (Eccl. Hist.)
   One of a sect of mystics originated in the seventeenth
   century by Molinos, a Spanish priest living in Rome. See
   Quietism.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quietist
    n 1: a religious mystic who follows quietism