Used only in Galatians 4:24, where the apostle refers to the history of Isaac the free-born, and Ishmael the slave-born, and makes use of it allegorically.
Every parable is an allegory. Nathan (2 Samuel 12:1-4) addresses David in an allegorical narrative. In the eightieth Psalm there is a beautiful allegory: "Thou broughtest a vine out of Egypt," etc. In Eccl 12:2-6, there is a striking allegorical description of old age.
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain, copy freely.
Easton, Matthew George. "Entry for 'Allegory'". "Easton's Bible Dictionary".