The phrase "gave go-ahead" means to grant permission or approval for something. Antonyms for this phrase would include words such as "forbid," "prohibit," "deny," "refuse," "reject," and "disapprove." These words convey the opposite meaning of "gave go-ahead," as they suggest the act of withholding permission or denying approval. In some cases, the phrase "held back" may also be used as an antonym for "gave go-ahead," as it implies the act of not giving approval or permission. When using language, it is important to consider the antonyms of words and phrases to ensure clear communication and avoid misunderstandings.