Horse's mouth is an idiom used to refer to information obtained firsthand from a reliable source. The antonyms for this phrase can be indirect, unreliable or secondhand sources. Such sources can include rumors, gossip, hearsay, or unverified reports. Other antonyms can include biased, edited, or incomplete information. The opposite of a "horse's mouth" can also be impersonal, anonymous sources such as news articles or anonymous tips with unknown sources. Therefore, when seeking accurate information, it is essential to rely on credible and trustworthy sources rather than ambiguous or incomplete ones.