buttstock

or butt-stock

[ buht-stok ]
/ ˈbʌtˌstɒk /

noun

the part of the stock located behind the breech mechanism of a firearm.

Origin of buttstock

First recorded in 1905–10; butt1 + stock
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019