/ ˈerənt; NAmE / adjective [ only before noun ] ( formal or humorous )
1.
doing sth that is wrong; not behaving in an acceptable way ( figurative )
2.
( of a husband or wife ) not sexually faithful
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WORD ORIGIN
Middle English (in the original sense, travelling in search of adventure): the current sense is from Latin errant- erring, from the verb errare . Compare with arrant .