hypercorrectly

/ˌhaɪpərkəˈrɛktli/
adverb
  1. In a way that shows an overly careful or exaggerated effort to follow a rule of grammar, pronunciation, or social behavior, often resulting in an unnatural or incorrect form.
    • She hypercorrectly said 'whom' instead of 'who' in every sentence, even when it was wrong.
    • He hypercorrectly pronounced the 't' in 'often' to sound more formal, though most people don't say it.
    • The student hypercorrectly avoided ending any sentence with a preposition, making his writing sound stiff.