1. Something that is very surprising. The phrase refers to how the eyes tend to widen when one is surprised. A: "Wow, these results are really an eye-popper." B: "I know, I didn't expect the experiment to turn out like this."
2. A very attractive woman. You said my date would be pretty, but dang—she's an eye-popper!
eye-popper
1. n. something astonishing. (Alludes to the comical view of eyes bulging outward in surprise or amazement.) What an eye-popper of a story!
2. n. a very good-looking woman or girl. Isn’t that foxy lady an eye-popper?