Chem.
a white, deliquescent, water-soluble solid, NaOH, usually in the form of lumps, sticks, chips, or pellets, that upon solution in water generates heat: used chiefly in the manufacture of other chemicals, rayon, film, soap, as a laboratory reagent, and in medicine as a caustic. Also called caustic soda, soda .
[ 1880-85 ]