v (transitive) To treat with bleach, especially so as to whiten (fabric, paper, etc) or lighten (hair).
v (intransitive|biology|of corals) to lose color due to stress-induced expulsion of symbiotic unicellular algae.
n (uncountable) A chemical, such as sodium hypochlorite or hydrogen peroxide, or a preparation of such a chemical, used for disinfecting or whitening.