slang Directly from the person or place where it began; from a reliable source or a person that cannot be doubted. They are going to be married. I got the news straight from the horse's mouth their minister. John found out about the painting straight from the horse's mouth, from the painter himself.
STRAIGHT FROM THE HORSE'S MOUTH
Meaning of STRAIGHT FROM THE HORSE'S MOUTH in English
American idioms English vocabulary. Английский словарь американских идиом. 2012