optimise

from WordNet (r) 3.0 (2006)

optimise
    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}]

from The Collaborative International Dictionary of English v.0.48

optimise \op"ti*mise`\ ([o^]p"t[i^]*m[imac]z`) v. t.
   Same as {optimize}. [Chiefly Brit.]
   [PJC]

from The Free On-line Dictionary of Computing (8 July 2008)

optimise

   To perform {optimisation}.