To produce a frothy white mass of bubbles, typically by mixing soap with water. She lathered the soap between her hands before washing her face.
To cover or smear with a thick layer of a substance. He lathered the bread with butter before toasting it.
To apply a substance in a thick, frothy layer. The barber lathered the customer's face before shaving.
(of a horse or other animal) to sweat so much that a white froth forms on the skin, or to cause an animal to do so. The rider had lathered the horse by pushing it too hard.
(Informal) To beat or thrash soundly. The older boys threatened to lather him if he snitched.