Definition of 'Call'
1. The period of time between the opening and closing of some future markets wherein the prices are established through an auction process.
2. An option contract giving the owner the right (but not the obligation) to buy a specified amount of an underlying security at a specified price within a specified time.
Investopedia explains 'Call'
1. In some exchanges, the call period is an important time in which to match and execute a large number of orders before opening and closing.
2. A call becomes more valuable as the price of the underlying asset (stock) appreciates.