window

1. A band in the electromagnetic spectrum that offers maximum transmission and minimal attenuation through a particular medium with the use of a specific sensor.

See atmospheric window.

1. Open water in a predominantly frozen river.
   It is caused by warmer water from a spring or tributary, or by turbulence over a shoal. See polyn’ya.
2. (Obsolete.) A term for the chaff used for military countermeasure purposes during World War II.