drop window

noun

a window with a sash that slides into a space below the sill.

Origin of drop window

First recorded in 1900–05

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for drop window

Historical Examples of drop window

A shelf or counter can be fitted inside the drop-window for the display of your wares.
Woodworking for Beginners
Charles Gardner Wheeler