mullion /ˈmʌlɪən/

• 1.  

  N（名词） a vertical member between the casements or panes of a window or the panels of a screen (窗户等的)竖框
• 2.  

  V（动词） to furnish (a window, screen, etc) with mullions 给(窗户、屏幕等)加竖框