1. Common stock issued by a parent company that tracks the performance of a particular division without having claim on the assets of the division or the parent company. Also known as "designer stock". 

2. A type of security specifically designed to mirror the performance of a larger index.

Investopedia Says:
1. When a parent company issues a tracking stock, all revenues and expenses of the applicable division are separated from the parent company's financial statements and bound to the tracking stock. Oftentimes, this is done to separate a subsidiary's high-growth division from a larger parent company that is presenting losses. The parent company and its shareholders, however, still control the operations of the subsidiary.

2. The most popular tracking stock is the QQQQ, which is an exchange-traded fund that mirrors the returns of the Nasdaq 100 index. Another type of tracking stock is Standard & Poor's depository receipts (SPDRs), which mirror the returns of the S&P 500 index.

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