Definition of mullions:
(n) :
(architecture) A vertical bar between the panes of glass or casements of a window or the panels of a screen.
(v) :
(transitive) To shape into divisions by means of mullions.
(n) :
A village and civil parish in south-west Cornwall, England (OS grid ref SW6719).
(n) :
A locality in Yass Valley council area, Southern Tablelands, New South Wales, Australia.