discretionary

1. Left to or regulated by one's own discretion or judgment.
2. Available for use as needed or desired: a discretionary fund.

adjective

1. Based on individual judgment or discretion: arbitrary, judgmental, personal, subjective. See opinion, surprise/expect.
2. Not compulsory or automatic: elective, facultative, optional. See choice.

Definition: open to choice
Antonyms: nondiscretionary

The adjective has 2 meanings:

Meaning #1: having or using the ability to act or decide according to your own discretion or judgment
  Synonym: discretional

Meaning #2: (especially of funds) not earmarked; available for use as needed