X engine
![X-engine according to US Patent 1889583 (Eingetragen 1928)[1]](/uploads/202502/21/2A-2775-Fig_25641.jpg)

An X engine is a piston engine comprising twinned V-block engines horizontally opposed to each other. Thus, the cylinders are arranged in four banks, driving a common crankshaft. Viewed head-on, this would appear as an X. X engines were often coupled engines derived from existing powerplants.