The term 'PREFIX WITH -NAUT' can be solved by the crossword solutions ASTRO (5 letters) and AERO (4 letters). ASTRO is a prefix meaning 'STAR' or 'astronomy', while AERO is a prefix meaning 'AIR' or 'AERONAUTICS'. Both of these terms, when combined with the suffix '-naut', create words that refer to someone who travels in space or AIR. Therefore, ASTRO-NAUT refers to an astronaut, and AERO-NAUT refers to an aeronaut.