Noun
skewback (plural skewbacks)
(architecture) The side of an arch; the course of masonry on the top of an abutment with a slope for the base of the arch to rest against.
As in the scimitar blades used on some aircraft, the blade tips of a skewback propeller are swept back against the direction of rotation. Source: Internet
Skewback propeller An advanced type of propeller used on German Type 212 submarines is called a skewback propeller. Source: Internet