theo ‧ rist AC /ˈθɪərəst, ˈθɪərɪst $ ˈθiːə-/ BrE AmE ( also theo‧re‧ti‧cian /ˌθɪərəˈtɪʃ ə n $ ˌθiːə-/) noun [countable]
[ Word Family: noun : ↑ theorist , ↑ theory , ↑ theorem , theoretician; verb : ↑ theorize ; adverb : ↑ theoretically ; adjective : ↑ theoretical ]
someone who develops ideas within a particular subject that explain why particular things happen or are true:
a leading economic theorist