Mot"to (?), n.; pl. Mottoes (#). [It. motto a word, a saying, L. muttum a mutter, a grunt, cf. muttire, mutire, to mutter, mumble; prob. of imitative origin. Cf. Mot a word.]
1. Her.
A sentence, phrase, or word, forming part of an heraldic achievment.
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.
© Webster 1913.