iotacism

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. In Greek, the pronunciation of certain letters, like eta and upsilon, as iota (ē) because of a regular sound change.

Century Dictionary and Cyclopedia

1. n. Conversion of other vowel sounds into that of iota (English ē); specifically, in pronunciation of Greek, the practice of giving the sound of iota (ι) also to the vowels η and υ, and to the diphthongs ει, ῃ, οι, and υι indiscriminately. This is the rule in modern Greek. Also called itacism. Opposed to etacism. Compare lambdacism, rhotacism.

Wiktionary

1. n. A misspelling resulting from such pronunciation.

GNU Webster's 1913

1. n. The frequent use of the sound of iota (that of English e in be), as among the modern Greeks; also, confusion from sounding ε, ι, η, υ, ει, etc., like ι.