Definition of lumpers:
(n) :
An extra laborer hired to assist in the loading or unloading of a truck or a ship.
(n) :
(biology, linguistics) A scientist in one of various fields who prefers to keep categories such as species or dialects together in larger groups.
(n) :
(dialect) A militiaman.
(n) :
(dialect) A lamprey.
(n) :
(historical) Synonym of lumpman (“type of salt worker”).
(v) :
(intransitive, archaic) To lumber; to plod.