Canadian raising

noun2

1. •
   The phenomenon in some dialects of English, especially Canadian English, in which /aɪ/ is realized as [ʌɪ] and/or /aʊ/ is realized as [ʌʊ] or [ɛʊ] before underlying unvoiced consonants.
2. •
   A similar but more restricted phenomenon, found in most dialects of American English, that applies only to /aɪ/, which is realized as [ʌɪ] in certain contexts, especially before underlying unvoiced consonants but with significant speaker-to-speaker variation.