"tank"
http://photobucket.com/albums/y198/tank666/?action=view¤t=Picture001.jpg
Many Asian countries use squatting type toilets, where the user squat over a water trench and water would wash the bio-mass down into the septic tank. These types of toilets in China are called 糞槽 (feces trench) or 尿槽 (urine trench).
The character 槽 may also mean “tank”, “trough”, and “groove” depends on context.
I had a good laugh when a reader emailed in his friend’s tattoo (see above) and said his friend wanted “tank” (military type, not the toilet kind) on him because he liked military tanks and he is a big guy.
By the way, “tank” (military type) in Chinese is 坦克 or 戰車, and 戦車 in Japanese.