The term 'prefix with PHYSICIST' can be solved by two crossword solutions: ASTRO and GEO. ASTRO is a 5-letter word meaning 'relating to astronomy or outer space', while GEO is a 3-letter word meaning 'relating to the Earth'. Both words are prefixes that can be used in combination with the word 'PHYSICIST' to form new words, such as 'astrophysicist' and 'geophysicist'. Astrophysicists study the physical properties of celestial bodies, while geophysicists study the physical properties of the Earth.