fanlight

As a noun fanlight

is a semicircular or semioval window over a door or other window, normally having a fan-like structure of ribs; sometimes hinged to the transom.

As an adjective undefined is

lacking a definition or value.

As nouns the difference between fanlight and toplight

is that fanlight is a semicircular or semioval window over a door or other window, normally having a fan-like structure of ribs; sometimes hinged to the transom while toplight is (nautical) a lantern or light on the top of a vessel.

As nouns the difference between taxonomy and fanlight

is that taxonomy is the science or the technique used to make a classification while fanlight is a semicircular or semioval window over a door or other window, normally having a fan-like structure of ribs; sometimes hinged to the transom.