The definition of a witch is a woman thought to be able to cast spells or possess magical powers, or the term connotes evil and can also be used to describe a mean old woman.(noun)
See witch in Webster's New World College Dictionary
Origin: ME wicche < OE wicce, fem. of wicca, sorcerer, akin to MDu wicken, to use magic < IE base *weik-, to separate (hence set aside for religious worship) > Goth weihs, holy, OE wig, idol
See witch in American Heritage Dictionary 4
Origin: Middle English wicche
Origin: , from Old English wicce, witch
Origin: , and wicca, wizard, sorcerer; see weg- in Indo-European roots.
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