A barrier to which a barrier option is subject for a period (window) shorter than the option’s term. In other words, the option with a window barrier (known as a window barrier option) is only observed for barrier breach in either way or both during part of its life, rather than its entire lifespan. The window observation period is a restricted time period, during which is the underlying price/ rate or variable is monitored for hits. The monitory period can be right at the commencement of an option’s life, or may start any time later on and continues till its maturity date.

A window barrier is also known as a partial barrier (in which case, the option is called a partial barrier option).