The Collaborative International Dictionary
By halves
Halves \Halves\ (h[aum]vz), n., pl. of Half.
By halves, by one half at once; halfway; fragmentarily; partially; incompletely.
I can not believe by halves; either I have faith, or
I have it not.
--J. H.
Newman.
To go halves. See under Go.
Wiktionary
by halves
adv. (context idiomatic English) partially, incompletely; inadequately, halfheartedly, shoddily.