noun
A guard dog.
(figurative) An individual or group that monitors the activities of another entity (such as an individual, corporation, non-profit group, or governmental organization) on behalf of the public to ensure that entity does not behave illegally or unethically.
(electronics, computing) Ellipsis of watchdog timer.
verb
To perform a function analogous to that of a watchdog; to guard and warn.
(electronics) To be continuously reset by a watchdog timer.