What we frequently refer to here as a "rational agent" isn't an optimized agent, it's an optimizing agent -- one that makes the decisions that most effectively implement its goals.

I am reminded of one of the early videos in Norvig and Thrun's recent online AI class, where "optimal" was used in two different senses in rapid succession — to mean "the algorithm yields the shortest route" and "the algorithm executes in the best time". This yielded some confusion for a friend of mine, who assumed that the speaker meant that these were both aspects of some deeper definition of "optimal" which would then be explained. No such explanation was forthcoming.