One who, or that which, plumps or swells out something else; hence, something carried in the mouth to distend the cheeks.
(English Elections) A vote given to one candidate only, when two or more are to be elected, thus giving him the advantage over the others. A person who gives his vote thus is said to plump, or to plump his vote.
A voter who plumps his vote. (Eng.)
A downright, unqualified lie. (Colloq. or Low)