The term 'Nautical Prefix' refers to words that are used to describe something related to the sea or sailing. The two crossword solutions for this term are AERO (4 letters) and ASTRO (5 letters). AERO is derived from the Greek word for air, and is used to refer to things related to the atmosphere or aviation. ASTRO is derived from the Greek word for star, and is used to refer to things related to outer space or astronomy.