Definitions
There are 2 meanings of the phrase
By Word Of Mouth.
By Word Of Mouth - as an adverb
Orally
Example: "I heard it viva voce"
By spoken rather than written means
Example: "These stories were transmitted by word of mouth"
Example Sentences
"They heard about the job opportunity by word of mouth."
"The news spread quickly by word of mouth."
"The rumor was passed on by word of mouth."
"The product gained popularity solely by word of mouth."
"They learned the secret recipe by word of mouth."