from The Century Dictionary.
- noun A high and narrow window, terminating in an arch acutely pointed or formed of curves of long radius (the center falling outside of the arch), and resembling a lancet in shape.
Sorry, no etymologies found.
Jack Spraggon coming after all? 'added he, drawing out a telescope and opening a lancet-window.
a step or two; of odd nooks and sombre little corridors, and tiny apartments squeezed aside into corners, and lighted either from the corridor or by a lancet-window or a loophole.