悪水[akusui] undrinkable water
井戸水[idomizu] well water
一衣帯水[ichiitaisui] (being separated only by a) narrow strip of water
一水[issui] current (of water)
溢水[issui] inundation

飲水量[insuiryou] amount of drinking
飲料水[inryousui] drinking water
烏の行水[karasunogyouzui] quick bath
雲水[unsui] itinerant priest
塩化水素[enkasuiso] hydrogen chloride

ミサイル防衛[misairubouei] missile defence
共同防衛[kyoudoubouei] joint defense
攻防[koubou] offense and defense
攻防戦[koubousen] battle
国防[kokubou] national defence

国防総省[kokubousoushou] National Military Establishment
国防長官[kokubouchoukan] Secretary of Defence (Defense)
国防費[kokubouhi] defence expenditure
砂防[sabou] erosion control
酸化防止剤[sankaboushizai] antioxidant