a counterweight to a vertically sliding window sash.
Origin of sash weight
First recorded in 1730–40
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
a weight used to counterbalance the weight of a sliding sash in a sash window and thus hold it in position at any height
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012