(Apple; originally from the introduction to Tom Lehrer's song "It Makes A Fellow Proud To Be A Soldier") Used ironically to indicate the speaker's lack of the quantity in question; a mythical schedule slot for accomplishing tasks held to be unlikely or impossible. Sometimes used to indicate that the speaker is interested in accomplishing the task, but believes that the opportunity will not arise. "I'll implement the automatic layout stuff in my copious free time."
The phrase is also used for time reserved for bogus or otherwise idiotic tasks, such as implementation of bad chrome, or the stroking of suits. "I'll get back to him on that feature in my copious free time."