The Collaborative International Dictionary of English v.0.48:

Discretional \Dis*cre"tion*al\, Discretionary
\Dis*cre"tion*a*ry\, [Cf. F. discr['e]tionnaire.]
   Left to discretion; unrestrained except by discretion or
   judgment; as, an ambassador with discretionary powers.
   Discretionally

WordNet (r) 3.0 (2006):

discretionary
    adj 1: having or using the ability to act or decide according to
           your own discretion or judgment; "The commission has
           discretionary power to award extra funds" [syn:
           discretionary, discretional]
    2: (especially of funds) not earmarked; available for use as
       needed; "discretionary funds"; "discretionary income"

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "discretionary":
   arbitrary, autonomous, discretional, elective, free, free will,
   gratuitous, independent, nonmandatory, offered, optional,
   proffered, self-acting, self-active, self-determined,
   self-determining, spontaneous, unasked, unbesought, unbidden,
   uncalled-for, uncoerced, uncompelled, unforced, uninfluenced,
   uninvited, unpressured, unprompted, unrequested, unrequired,
   unsolicited, unsought, voluntary, volunteer, willful