1. A substance that is usually white and made by rapidly stirring soap and water resulting in small bubbles or foam: When Sherrie washes her hair, she uses warm water and applies shampoo and then she massages it into a rich lather.
2. Etymology: from Greek, louein, "to bathe" then from Latin lavere, "to wash".

"In old English, this term was recorded as meaning, "washing soda", and the modern meaning of "soap bubbles" came into existence in about the late 16th century."

A white mass of bubbles that is produced with a mixture of soap and water: Earl lathered his face with shaving cream which softened his three-day beard so he could shave it off easier.