Powerlinx

The term powerlinx has several different meanings, most of which have to do with robots combining with one another. In the Armada franchise, powerlinxing was the act wherein a Mini-Con attached to a Bulk, adding a boost of extra power to the larger robot.

In the Energon franchise, powerlinxing was the process by which two similarly sized Autobots combined (via the Spark of Combination) into a single, more powerful robot.

Cyber Planet Keys do not Powerlinx. Well, except Demolishor's. And deluxe Optimus Prime's.

From Teletraan I: The Transformers Wiki, a Wikia wiki.