What is another word for that would be telling?
Pronunciation: [ðat wʊd biː tˈɛlɪŋ] (IPA) 
The phrase "that would be telling" is often used to indicate that the speaker is not willing to share certain information or secrets. Some synonyms for this phrase include "I can't say," "I'm not at liberty to say," "I'm sworn to secrecy," "it's confidential," "I promised not to say," and "I'm not authorized to disclose." These phrases are commonly used in situations in which the speaker wants to maintain privacy and confidentiality, such as in business or legal settings. Using alternative expressions can help avoid awkward or uncomfortable conversations, while also preserving friendships and relationships.
