A Witch is Generally
A person who engages in earth-based, elemental, or practically/physically grounded magic or magical thinking, often according to a system of rules or guidelines. Magical thinking is generally defined as thought or belief that links actions, expressions, or creations with specific events, though there is no scientific (or, for our purposes, canonical) basis for such.
A Witch Might Be
Of any sex, gender, sexual orientation, or gender orientation.
Of any race or, sometimes, species.
A member of the Wiccan religion.
A pagan.
A practictioner of magic
...or sometimes of magick.
A figure in folklore or fairy tales
A character in a play.
A person who self-identifies as a witch.
A Witch Is Not Necessarily
A woman
... either young and alluring
... or old and haglike.
Always
Chaotic Evil... or
Lawful Good.A member of a specific race or culture
Pre-industrial, third-world, or otherwise unfamiliar or unused to or eschewing technology.
A visibly magical person.
A practitioner of Wicca or paganism.
A wise person.
Basically...
Witches include the first two descriptions, but are not limited to the last.