D defs.my
Entry 2 senses Webster, 1913

Optimist

/äp'-təm-ĭst/ · Op·ti·mist · IPA /ˈɑptɪmɪst/
01 n. One who holds the opinion that all events are ordered for the best.
  1. 1.
    One who holds the opinion that all events are ordered for the best.(Metaph.)
  2. 2.
    One who looks on the bright side of things, or takes hopeful views; one who experiences optimism{2}; -- opposed to pessimist.