Boyd’s Bible Dictionary:

Concise Bible Dictionary:

The word ἀλληγορέω, occurs only in Galatians 4:2424Which things are an allegory: for these are the two covenants; the one from the mount Sinai, which gendereth to bondage, which is Agar. (Galatians 4:24). The passage does not mean that Abraham having two sons was an allegory: it was history, but that history had an allegorical application, which Paul, by the Holy Ghost, fully explains. The Greek word signifies “to speak otherwise,” and an allegory is a description of one thing under the image of another.