An argument in which an equivocal expression is used in one sense in
one premise and in a different sense in another premise, or in the
conclusion. Equivocal means (1) of uncertain significance; not
determined, and (2) having different meanings equally possible.
Equivocation is a type of Fallacy of Ambiguity. The opposite of
equivocation is "unovocation," in which a word always carries the same
meaning through a given context.