service dog

Short definition from Wiktionary

Noun

1. 1
   A dog that serves humans by helping them with activities of daily living, with search and rescue, or with other (non-draft and non-farming) tasks: A dog that assists a person who has a physical disability or has a mental disability such as post-traumatic stress disorder.
2. 2
   A dog that serves humans by helping them with activities of daily living, with search and rescue, or with other (non-draft and non-farming) tasks: A dog which assists the work of military or law enforcement officials.