| Rating | Solver | Clue |
|---|---|---|
| OBSERVABLE | Perceivable | |
| VIEWLESS | Not perceivable by the eye; invisible; unseen. | |
| PERCEPTIBLE | Capable of being perceived; cognizable; discernible; perceivable. | |
| VISIBLE | Perceivable by the eye; capable of being seen; perceptible; in view; as, a visible star; the least spot is visible on white paper. |