1. In geology, a rock consisting of pebbles and gravel embedded in cement; pudding stone: A conglomerate is a composite rock incorporating matter of different sizes, like minerals.
2. A corporation made up of a number of different companies that operate in diversified fields: Sally's new kitchen was created by a conglomerate consisting of diverse companies that installed the different necessary items, like the plumbing, electrical attachments, the flooring, appliances, etc.
3. An item made up of heterogeneous substances or individuals: Toronto is made up of a conglomerate of people of many different nationalities.

1. To form or gather into a mass or whole: When mixing the dough for the cake in a mixing bowl, it conglomerated into one big lump.

Over the months, the town's trash conglomerated in the ravine close to the stream.
2. To form into or merge with a corporate conglomerate: The small company decided to conglomerate with the larger one in the big city.

A water-deposited composite rock containing more than 50% volcanic material: A volcanic conglomerate consists particularly of coarse pyroclastics.