“A composition that is continually used in repertoires.”
American Heritage Dictionary of the English Language, Fourth Edition, Houghton Mifflin company 2000 ISBN 0-395-82517>p>
“A musical piece of sufficiently enduring popularity to be made part of a permanent repertoire, especially a popular song that is held in continuing esteem and is commonly used as the basis of jazz arrangements or improvisations.”
The Unabridged Random House Dictionary 1967 Random House, Inc.
“A standard is a popular song that is well known, frequently performed, and remains in the popular repertoire for at least several years.”
Enjoying Jazz by Henry Martin Schirmer Books, 1986 ISBN 0-02-873130-1
“Composition or song that has, by dint of its lasting memorability and general worth, become a regularly used item in some field of music -a jazz standard, for example.”
The Oxford Companion to Popular Music 1991, Peter Gammond, Oxford University Press, ISBN 0-19-311323-6