rigol or rigoll /rigˈəl/

1. A gutter or water channel
2. A groove, esp an encircling groove
3. A circlet (Shakespeare)

• optical telescope
• optical tweezers
• optic axes
• optic axis
• optic disc
• optic discs
• optician
• opticians
• optic lobe
• optic lobes
• optic nerve
• optic nerves
• optics
• optic thalamus
• optic tube
• optima
• optimal
• platen
• platens
• plate-powder
• plate-printing
• plate-proof
• plate-proofs
• plater
• plate rack