n. 1 any of various compounds of sodium in common use, e.g. washing soda, caustic soda. 2 (in full soda water) water made effervescent by impregnation with carbon dioxide under pressure and used alone or with spirits etc. as a drink (orig. made with sodium bicarbonate). 3 esp. US a sweet effervescent drink. soda bread bread leavened with baking-soda. soda fountain 1 a device supplying soda water. 2 a shop or counter equipped with this. soda lime a mixture of calcium oxide and sodium hydroxide.
[ med.L, perh. f. sodanum glasswort (used as a remedy for headaches) f. soda headache f. Arab. suda' f. sada' a split ]