When an industrial facility that consumes a copious volume of water suddenly stops drawing water from a water treatment plant via a pneumatic switch or quick-close valve. The instantaneous closing of the valve causes a backup of water pressure that breaks water treatment plant pumps and pipes.
The water treatment plant's pumps were destroyed when a chicken plant slammed their valve closed after a washdown of the facility causing a water hammer
Something engineers, mainly Machinist Mates, do in the U.S. Navy to each other in the boiler/engineering room. A container of water is dumped from an upper level area to someone on the lower level, or from any high area to any lower area. It is always meant to be a surprise. It is also done to people who are sleeping on watch as a way to wake them up, and they do so in shock, to teach them to not sleep on watch or else it will happen again. It is also done to people who are already awake as a practical joke. Something like that would usually never be done to any higher-ups, especially those that don't participate in the game, since it will get you in trouble.
Petty Officer Clark: You see Price sleeping in the sscape exit? Let's water hammer him!
Petty Officer Price: I just got water hammered. Do you know who did it?
Fireman Stovell: Yes, it was Clark.
Petty Officer Price: I'm gonna water hammer him next chance I get! It's on now!
1) when you turn off the faucet or shower and it makes a loud banging sound
2) when you get a chick so wet that it's like banging a bag of water
I got this chick so wet by playing with her tits, it was like waterhammering when we finally got down to it.