Refers to the ceiling and floor of the price fluctuation of an underlying asset. A collar is usually set up with options, swaps, or by other agreements. In corporate finance, the collar strategy of buying puts and selling calls is often used to mitigate the risk of a concentrated position in (sometimes) restricted stock. When the restricted owner can't sell the stock, but needs to diversify the risk, a collar transaction is one of the few tools available. Many corporate executives who receive chunks of their compensation in restricted stock need to employ this strategy to mitigate the diversification risk in their overall portfolio.