the.com/lancet window

means A tall, narrow window topped with a sharp pointed arch, typical of early Gothic architecture.

from Named simply for its shape, a lance — that slender spear with its tapering point. The word 'lancet' itself comes via Old French 'lancette', a diminutive of 'lance', from Latin 'lancea' (spear). The term was borrowed into architecture to describe the thin, blade-like arch that defines the style, especially in English Gothic buildings from the 12th and 13th centuries, where rows of these windows were often grouped together, most famously in the 'Five Sisters' window of York Minster.