word of mouth
The verbal sharing of information. A: "How did you hear about our bakery?" B: "Oh, word of mouth. My dad told me about it." We don't have the budget for a big marketing campaign, so we'll just have to hope that buzz about our shop gets spread by word of mouth.
word of mouth
spoken language; informal or unofficial discourse. 1987 Bruce Duffy The World As I Found It His ideas were repeated by word of mouth or passed around as transcripts of the shorthand notes that his students doggedly took down during his lectures.
word of mouth, by
Orally. This phrase dates from the sixteenth century and persists to the present, though simply “orally” would be more direct. “A little message unto hir by worde of mouth,” wrote Nicholas Udall in Ralph Roister Doister (ca. 1553), presumably differentiating it from a written message.