None of the options provided specifically describe a "homophobic pun." A homophobic pun would typically be a play on words that incorporates themes or ideas that are derogatory or offensive toward LGBTQ+ individuals, using humor to perpetuate stereotypes or discrimination.
However, among the options you've given, the first one—"a pun that uses two words that sound the same but have different meanings"—is the most related to the general concept of a pun. Just to clarify, a homophobic pun would still be a pun that fits this definition, but it would also carry negative connotations related to homophobia.