Real Dictionary

lather
singular noun: A lather is a white mass of bubbles which is produced by mixing a substance such as soap or washing powder with water.
verb: If you lather something, you rub a substance such as soap or washing powder on it until a lather is produced, in order to clean it.
verb: When a substance such as soap or washing powder lathers, it produces a white mass of bubbles because it has been mixed with water.

lather in American English
the foam or froth formed by soap or other detergent in water
to cover with lather
to form, or become covered with, lather

lather in American English 1
intransitive verb: to form a lather
noun: foam or froth made by a detergent, esp. soap, when stirred or rubbed in water, as by a brush used in shaving or by hands in washing
transitive verb: to apply lather to; cover with lather

lather in American English 2
noun: a worker who puts up laths

lather in British English
noun: foam or froth formed by the action of soap or a detergent in water
verb: to coat or become coated with lather