wittol
A man who knows and tolerates his wife's infidelity with another man or men; a mari complaisant.
archaic
To see […] a wittol wink at his wife's honesty, and too perspicuous in all other affairs […]
A bird, the wheatear.
obsolete
Where it comes from
From Middle English witewold; likely a blend of witen (“to know”) + cockewold (“cuckold”), equivalent to wit + cuckold.
Adapted from the Wiktionary entry wittol (CC BY-SA 4.0).