A window barrier option that has a vanilla payoff at expiration and is subject to a single or double American barriers over a rear part of its lifespan (the rear window), that is, the observation period starts at a certain point in time after the option’s inception date and ends at expiration date. For example, if the option’s life is 1 month, a rear window might mark the period between the beginning of second week and expiration date.

Like its origin, this option has many variations including those with up barrier, down barrier, knock-in, knock-out, double barrier, etc.

This option is also known as a late starting barrier option.