Meaning

noun harvester that heads and threshes and cleans grain while moving across the field

noun a consortium of independent organizations formed to limit competition by controlling the production and distribution of a product or service

noun an occurrence that results in things being united

originFrom combine, referring to the merger and purchase of various underground railway, tram and bus companies in London, combining them into one organisation. Originally applied to Underground Electric Railways of London Company Ltd, since used for successor organisations.

Etymology from Wiktionary, CC BY-SA 3.0