The phrase "delisting" refers to the withdrawal of a company's securities from a stock market. The securities of that corporation would no longer be traded on that stock exchange as a result of delisting.
There are two grounds for a company's delisting: forced or voluntary.

Forced delisting - When the exchanges decide to delist a company, usually due to non-compliance, this is known as a forced delisting. If you own shares in such businesses, you'll have to write them off as a terrible investment.

Delisting shares voluntarily - This occurs when the corporation decides to remove the shares from the exchange. This could be the result of a company reorganisation. In this case, the corporation will have to offer a premium above the current market price of the shares. Typically, the premium rises to 30-40% or higher.
In either case, when a company delists, its shares are renounced and are no longer traded on the stock exchanges.