1) Tapering at the tip 
• (a.) Narrowed at the forward end; -- said of an automobile frame when the side members are closer together at the forward end than at the rear.
In'swept` adjective Narrowed at the forward end; -- said of an automobile frame when the side members are closer together at the forward end than at the rear. 
tapering or narrowing at the front or tip, as an airplane wing.