a substance used to cleanse and emulsify (stabilize oil-and-water mixtures) that lathers when rubbed in water and consists essentially of chemical salts formed by the combination of sodium or potassium combined with fatty acids

I write letters blatant on medicines patent … and vow my complexion derives its perfection from somebody's soap – which it doesn't — W S Gilbert

a chemical salt formed by the combination of a fatty acid with a metal

= soap opera

to rub soap over or into (something or somebody)

informal (often + up) to flatter (somebody)