The Collaborative International Dictionary of English v.0.48:

optimize \op"ti*mize`\ ([o^]p"t[i^]*m[imac]z`) v. t. [imp. & p.
   p. optimized ([o^]p"t[i^]*m[imac]zd`); p. pr. & vb. n.
   optimizing ([o^]p"t[i^]*m[imac]`z[i^]ng).]
   1. To make as useful, effective, or functional as possible;
      as, to optimize the speed of a computer program.

   Syn: optimise.
        [WordNet 1.5]

   2. To get the most out of; to use to the best effect; to
      exploit fully; as, to optimize one's return on investment.

   Syn: make optimal, optimise.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

optimize
    v 1: make optimal; get the most out of; use best; "optimize your
         resources" [syn: optimize, optimise]
    2: modify to achieve maximum efficiency in storage capacity or
       time or cost; "optimize a computer program" [syn: optimize,
       optimise]
    3: act as an optimist and take a sunny view of the world [syn:
       optimize, optimise]

The Free On-line Dictionary of Computing (30 December 2018):

optimize

   optimisation