ambiguous pronoun reference
A pronoun that could point to more than one antecedent, leaving the reader to guess.
Ambiguous reference occurs when a pronoun has two or more equally available antecedents and nothing in the grammar decides between them; vague reference occurs when a pronoun (often this or it) points at an entire idea rather than any single noun.
Examples
When John talked to Mike, he was angry — he could be John or Mike.
See also