"This blunderbuss style weapon has a very wide arc of shot enabling it to clear a room in just a couple of shots"
The Donderbus is a shotgun manufactured by Smoke Stack in SAS: Zombie Assault 4. Before it appeared in the game, there had been no official statement on it from Ninja Kiwi, but its image and name were found in a SWF file used by the game as of the August 26th, 2015 update. As of 9/15 update, the Donderbus appears in the collections. It currently costs 80 NK coins to purchase and comes with all the bonuses of weapons.
According to official description, it appears to have exceptionally wide spread (low accuracy), presumably more than that of 1887 Shockfield. While the Donderbus is considerably good in the low levels, its lack of damage makes it near useless in the higher levels, nightmare mode , or apocalypse mode considering this to be one of the worst of the weapons in the game.
Donderbus is Dutch for "blunderbuss."
This means that the Donderbus is based on the Blunderbuss shotgun.
Donderbus spread compared to other shotguns (taken from Zecretly Myztery)