per ‧ fec ‧ tion ‧ ist /pəˈfekʃ ə nəst, pəˈfekʃ ə nɪst $ pər-/ BrE AmE noun [countable]
[ Word Family: noun : ↑ perfection ≠ ↑ imperfection , ↑ perfectionist , ↑ perfectionism , ↑ perfectibility ; adjective : ↑ perfect ≠ ↑ imperfect , ↑ perfectible , ↑ perfectionist ; verb : ↑ perfect ; adverb : ↑ perfectly ≠ ↑ imperfectly ]
someone who is not satisfied with anything unless it is completely perfect:
Many top athletes are perfectionists who drive themselves to excel.
—perfectionist adjective
—perfectionism noun [uncountable]