mullion

English Thesaurus

1. a nonstructural vertical strip between the casements or panes of a window (or the panels of a screen) (noun.artifact)

hypernym	:	slip, strip,
definition	:	artifact consisting of a narrow flat piece of material (noun.artifact)

part meronym	:	window,
definition	:	a framework of wood or metal that contains a glass windowpane and is built into a wall or roof to admit light or air (noun.artifact)