In H. P. Lovecraft's The Case of Charles Dexter Ward, is Joseph Curwen a lich, as defined by Wikipedia?
Technically he could be called one
Defining Lich as:
In fantasy fiction, a lich (/ˈlɪtʃ/;1 sometimes spelled liche, cognate to Dutch lijk and German Leiche, both meaning "corpse") is a type of undead creature. Often such a creature is the result of a transformation, as a powerful magician or king striving for eternal life uses spells or rituals to bind his intellect to his animated corpse and thereby achieve a form of immortality.
And from the text:
His older aspect increased to a startling degree his resemblance to the Curwen portrait in his library; and Dr. Willett would often pause by the latter after a call, marvelling at the virtual identity, and reflecting that only the small pit above the picture’s right eye now remained to differentiate the long-dead wizard from the living youth.
Emphasis mine. The wikipedia even refers to him as an "undead sorceror":
Armed with this knowledge, Willett confronts Curwen at the asylum and succeeds in reversing the spell, reducing the undead sorcerer once again to dust, the dust that was mentioned at the start of the story.
So given the elements of death, sorcery and immortality - I don't see why not.
The only actual use of the word "lich" in the literature associated with Lovecraft is in August Derleth's (under a pseudonym) "The Extra Passenger." The usage there indicated a reanimated corpse, more intelligent than a zombie, but a corpse all the same. Derleth indicated the supernatural appearance of the corpse to the activity of a demon transporting it there, so it would more or less be an undead body that the intelligence and personality had not left.