The Collaborative International Dictionary of English v.0.48:

Profitable \Prof"it*a*ble\, a. [F. profitable.]
   Yielding or bringing profit or gain; gainful; lucrative;
   useful; helpful; advantageous; beneficial; as, a profitable
   trade; profitable business; a profitable study or profession.
   [1913 Webster]

         What was so profitable to the empire became fatal to
         the
         emperor.                                 --Arbuthnot.
   [1913 Webster] -- Prof"it*a*ble*ness, n. --
   Prof"it*a*bly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

profitably
    adv 1: in a productive way; "they worked together productively
           for two years" [syn: productively, fruitfully,
           profitably] [ant: fruitlessly, unproductively,
           unprofitably]