1. A watery, typically yellowish fluid stored in the bladder and discharged through the urethra. It is one of the body’s chief means of eliminating excess water and salt and also contains nitrogen compounds such as urea and other waste substances removed from the blood by the kidneys. (Google dictionary)
2. A typically sterile liquid by-product of the body secreted by the kidneys through a process called urination and excreted through the urethra. (wikipedia.org)
Liquid excrement consisting of water, salts and urea, which is made in the kidneys, stored in the bladder, then released through the urethra. (wiktionary.org)
Word origin: From Latin Urina, ae, f.