1. An introductory statement; preface or introduction: The preamble in Karl's book expressed what was being included in his history book.
2. A preliminary or introductory fact or circumstance: Frank's childhood in the slums was a preamble to his life of crime.
3. When capitalized, a Preamble is the introductory statement of the U.S. Constitution: This Preamble sets forth the general principles of American government and begins with the words, "We, the people of the United States, in order to form a more perfect union ... " , therefore a section at the beginning of a speech, a report, or a formal document that establishes what follows.
4. Etymology: from Latin praeambulus, "going in front"; from Latin pre- + ambulare "to walk".