Synonyms for Optimistic (same or very similar meaning)
WordNet sense 1 (expecting the best):
affirmative
WordNet sense 2 (characterized by or displaying affirmation or acceptance or certainty etc.):
positive
WordNet sense 3 (confidently optimistic and cheerful):
sanguine
WordNet sense 4 (pleasantly (even unrealistically) optimistic):
cheerful, upbeat
From the ODE community, based on WordNet
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