A tank, cistern, or other receiver for holding water.(noun)
The Century Dictionary (Public Domain)
Use "water-tank" in a sentence
"I might be walking down the track to the water-tank to lie in wait for a passing freight-train, when I would chance upon a bunch of "alki-stiffs.""
"And Tim Hagan, reading the same while they lay in the grass by some water-tank, branded forever the mind of Young Dick with the fact that honor beyond price was a matter of neither place nor caste and might outcrop in the palace on the height of land or in the dwelling over a grocery down on the flat."
"The fifth sailor, rifle in hand, was standing guard by the water-tank just for'ard of the mainmast."