interjection, noun, plural boos, verb, booed, boo⋅ing.| 1. | (used to express contempt or disapprobation or to startle or frighten). |
| 2. | an exclamation of contempt or disapproval: a loud boo from the bleachers. |
| 3. | to cry boo in derision. |
| 4. | to show disapproval of by booing. |

| BOO Bootes (constellation) |