The Collaborative International Dictionary of English v.0.48:
Gainful \Gain"ful\, a. Profitable; advantageous; lucrative. "A gainful speculation." --Macaulay. -- Gain"ful*ly, adv. -- Gain"ful*ness, n. [1913 Webster]WordNet (r) 3.0 (2006):
gainfully adv 1: in a gainful way; "are you gainfully employed now?"