What is Bid Rigging?

Legal Definition
Bid rigging is a form of fraud in which a commercial contract is promised to one party even though for the sake of appearance several other parties also present a bid. This form of collusion is illegal in most countries. It is a form of price fixing and market allocation, often practiced where contracts are determined by a call for bids, for example in the case of government construction contracts.

Bid rigging almost always results in economic harm to the agency which is seeking the bids, and to the public, who ultimately bear the costs as taxpayers or consumers.
-- Wikipedia
Legal Definition
When competitors increase prices of bids to customers. Its illegal. AKA bid suppression.