license or liberty taken by a poet, prose writer, or other artist in deviating from rule, conventional form, logic, or fact, in order to produce a desired effect.
Origin of poetic license
First recorded in 1780–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Also, artistic license. The liberty taken by a writer or artist in deviating from conventional form or fact to achieve an effect. For example, I've never seen grass or a tree of that color; but that's artistic license. [Late 1700s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.