noun
Only when written 小水
Formal or medical term for urine; cross-referenced with 小便, which is more common in everyday speech.
See also: 小便
検査のために小水を採取した。
We collected a urine sample for the test.
noun
small amount of water
Literally 'small water'; used in contexts like gardening, cooking, or describing a tiny quantity of water.
I give the potted plant a small amount of water.
小便 is the common, everyday word for urine; 小水 is more formal and often used in medical contexts.
Compound of 小 (small) and 水 (water). The 'urine' sense is a euphemistic extension, similar to English 'pass water'.