mullions is mullion's Plural Form

mullion

US [ˈmʌljən]
UK ['mʌljən]
  • n.【建】(窗门的)直棂
  • Web多格框
Plural Form:mullions  
n.
1.
【建】(窗门的)直棂,竖框
na.
1.
“munnion”的变体