sheepdog

Short definition from Wiktionary

Noun

1. 1
   Any of various breeds of dog used for herding sheep; an individual of such a breed.
2. 2
   Any of various breeds of dog used for guarding sheep; an individual of such a breed.
3. 3
   A chaperon; an adult who accompanies other people in a supervisory role.
4. 4
   A police officer.

Verb

1. 1
   To chaperon or shepherd.