Spitting image means looking exactly like another person, so similar that people do a double-take. If your teacher says you're the spitting image of your older sister, she means you two could almost be twins. The resemblance is remarkably strong and precise.

The phrase usually describes family resemblances: a daughter who's the spitting image of her mother, or a grandson who looks exactly like his grandfather did at the same age. But it works for anyone who bears an uncanny similarity to someone else. You might notice that your friend is the spitting image of a famous actor, or that a historical figure in a textbook looks just like your neighbor.

The expression emphasizes perfect likeness beyond ordinary similarity. It's stronger than saying two people “look alike.” When someone is the spitting image of another person, it's as if they were copied exactly, from facial features to expressions to mannerisms.