Definition of "aggregator"

An event aggregator facilitates a fire-and-forget model of communication. The object triggering the event doesn't care if there are any subscribers.

2013, Addy Osmani, Developing Backbone.js Applications, page 175

What we have seen in recent years is the emergence of the aggregator as the immediate customer of our traditional rail freight operating businesses, meaning that the future model is likely to feature rail freight companies with strong expertise in rail movement of freight, and aggregators with strong expertise in intermodal operation. Thus the final customer relationship (Tesco, Amazon, and so on) is increasingly likely to be owned by the aggregator rather than the rail freight company.

2021 October 20, Michael Holden, “Time for action... and a new plan to develop rail freight”, in RAIL, number 942, pages 38–39