houndstooth check or hound's-tooth checknoun

• oppress
• oppression
• oppressive
• opprobrious
• opprobrium
• oppugn
• ops
• -opsis
• opsonin
• -opsy
• opt
• opt.
• optative
• optic
• optical
• optical activity
• optical art
• optical character reader
• optical character recognition
• optical fibre
• optical glass
• optical illusion
• optical isomer
• optic axis
• optician