/ ˌʌndəˈhænd; NAmE -dərˈh-/ (also less frequent under·hand·ed / -ˈhændɪd; NAmE /) adjective
( disapproving ) secret and dishonest :
I would never have expected her to behave in such an underhand way.
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WORD ORIGIN
Old English in the sense in or into subjection, under control (see under- , hand ).