Answer Description

In a watering hole attack the attacker infects a website that is known to be commonly used by an organisation or industry. For example a specific industry news site to attack a business in that industry or the entire industry in general. With the knowledge that users frequent the website the attackers are able to target them with malware and if the attack is successful to install malicious software.

Wikipedia

Watering hole is a computer attack strategy in which an attacker guesses or observes which websites an organization often uses and infects one or more of them with malware. Eventually, some member of the targeted group will become infected. Hacks looking for specific information may only attack users coming from a specific IP address. This also makes the hacks harder to detect and research. The name is derived from predators in the natural world, who wait for an opportunity to attack their prey near watering holes.