limewater. n. 1. (Pharmacology) a clear colourless solution of calcium hydroxide in water, formerly used in medicine as an antacid. 2. (Elements & Compounds) a clear colourless solution of calcium hydroxide in water, formerly used in medicine as an antacid. 3. (Elements & Compounds) water that contains dissolved lime or calcium salts, esp calcium carbonate or calcium sulphate. (ˈlaɪmˌwɔ tər, -ˌwɒt ər). n.