Definition:  A figure of speech in which a term or phrase is compared with an unrelated thing without using like or as, as opposed to a simile.

Example from The Pearl:  "Kino had wondered often at the iron in his patient, fragile wife" (p.6-7).  Juana doesn't have iron in her, but her tolerance was as hard as iron.

Example by me:  She is a rose (unless she literally is a rose).