caster sugar or castor sugarnoun

• flatmate
• flat out
• flatpack
• flat race
• flat spin
• flat spot
• flatten
• flatten out
• flatter
• flattery
• flattie
• flat-top
• flatty
• flatulent
• flatus
• flatware
• flatways
• flatworm
• flatwoven
• flaunching
• flaunt
• flautist
• flavescent
• Flavian
• flavin