| 1. | a number of animals kept, feeding, or traveling together; drove; flock: a herd of cattle; a herd of sheep; a herd of zebras. |
| 2. | Sometimes Disparaging. a large group of people: The star was mobbed by a herd of autograph seekers. |
| 3. | any large quantity: a herd of bicycles. |
| 4. | the herd, the common people; masses; rabble: He had no opinions of his own, but simply followed the herd. |
| 5. | to unite or go in a herd; assemble or associate as a herd. |
| 6. | ride herd on, to have charge or control of; maintain discipline over: He rode herd on 40 students in each class. |

ride herd on
Keep close watch or tight control over, as in Aunt Martha is always riding herd on her bridge club, making sure they follow the rules. This idiom alludes to the cowboy who rides around a herd of cattle to keep them together. [Late 1800s]