Given that hyper- can mean 'excessive', it should be clear that hypercorrection is 'excessive correction', or amending something too far.
In the study of language, hypercorrection is the phenomenon when a speaker who has learned that one usage is considered 'wrong' transfers that knowledge mistakenly to another, similar but not identical, usage. For example, many informal British speakers do not distinguish the subjective and objective forms 'I' and 'me' with the care of formal English. Such a speaker may say "Me and him went to the pictures", where written and formal usage requires "He and I went...". So in a formal environment, such as a school English lesson, this may be corrected by a teacher ("Don't say 'Me and him': say 'He and I'"). This lesson may be absorbed imperfectly (it may have been taught unclearly or incompletely), and lead to hypercorrection with a preposition like 'between', which in formal English takes the objective form: "between you and me". A hypercorrecting speaker may formulate the thought this way, and then, remembering "Don't say 'Me and him': say 'He and I'", produce the incorrect phrase "
between you and I".
Hypercorrection can be in different areas of language - in grammar, as above; and in pronunciation. Some speakers of Northern accents, for example, who form the vowel of 'up' and 'cup', etc, as '-oo-' (IPA: /uː/) begin to hypercorrect, realising all occurrences of the letter 'u' with the sound of RP 'up' (/ʌ/)- even when RP speakers themselves realise it as '-oo-'. This results in such pronunciations as 'put' like the sound of the golf stroke the 'putt' (IPA: /pʌt/), 'cushion' as IPA: /kʌʃn/ and 'butcher' being pronounced as if it began with 'but' (IPA: /'bʌtʃ ər/.
- Hypercorrection can also be used for the phenomenon that speakers who aspire to a 'higher class' of speech may become even more careful and 'correct' than those who naturally speak the form of the language which is aimed at. Both forms of hypercorrection can become a source of amusement or derision to more 'educated' speakers.