GAINFUL
gainful, paid, paying
(adjective) yielding a fair profit
Source: WordNet® 3.1
Etymology 1
Adjective
gainful (comparative more gainful, superlative most gainful)
Contrary.
Disposed to taking advantage of.
Troublesome; fractious; hard to handle.
Etymology 2
Adjective
gainful (comparative more gainful, superlative most gainful)
Providing gain; profitable.
Source: Wiktionary
Gain"ful, a.
Definition: Profitable; advantageous; lucrative. "A gainful speculation."
Macaulay.
– Gain"ful*ly, adv.
– Gain"ful*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition