D defs.my
Entry 2 senses Webster, 1913

Motto

/mät'-ō/ · Mot·to · IPA /ˈmɑ.toʊ/
01 n. A sentence, phrase, or word, forming part of an heraldic achievment.
pl. Mottoes ((#))
  1. 1.
    A sentence, phrase, or word, forming part of an heraldic achievment.(Her.)
  2. 2.
    A sentence, phrase, or word, prefixed to an essay, discourse, chapter, canto, or the like, suggestive of its subject matter; a short, suggestive expression of a guiding principle; a maxim.
    “It was the motto of a bishop eminent for his piety and good works, . . . “Serve God, and be cheerful.”” Addison.