Search Result for "law of diminishing returns":
Wordnet 3.0

NOUN (1)

1. a law affirming that to continue after a certain level of performance has been reached will result in a decline in effectiveness; 



WordNet (r) 3.0 (2006):

law of diminishing returns
    n 1: a law affirming that to continue after a certain level of
         performance has been reached will result in a decline in
         effectiveness