What is the meaning of Watchdog?

A guard dog.

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.

Ellipsis of watchdog timer.

To perform a function analogous to that of a watchdog; to guard and warn.

To be continuously reset by a watchdog timer.

Source: wiktionary.org