On the grapevine is an idiom that means a piece of information that is spread through rumor or gossip. There are multiple synonyms that can be used to connote the same meaning, such as "word of mouth," "through the grapevine," "hearsay," or "gossip mill." These expressions are typically used in informal settings. In contrast, the equivalent term used in a professional context could be "disclosure" or "leak," which would suggest that the information was intended to be kept confidential. Regardless of the terminology used, it is essential to be aware of what you say because it could spread like wildfire.