Most developers have a intuitive understanding of what a large refactoring is. But it is difficult to come up with a simple definition.

Therefore there was a workshop on large refactorings at OT2003Conference. The results and a place for a wiki discussion are available: 
*** http://www.ot2003.org/scripts/wiki/?LargeRefactorings ( BrokenLink }

-- StefanRoock
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Also see BigRefactorings and BigRefactoringsAreHard.

External references:
 * http://csc.noctrl.edu/f/opdyke/OOPSLA2003/Lippert-PositionPaper-OOPSLA-2003-Workshop.pdf
 * http://www.refactoring.be/thumbnails/large/large.html

''Also see NoseJobRefactoring. Could we conclude that all nose-jobs are "big"?  It isn't obviously true that all BigRefactorings are nose-jobs.''