This appears to be a proper name (typically Irish surname) rather than a common English word; without additional context, it doesn't have a standard dictionary definition.
Meehan is an Irish surname, possibly derived from 'Ó Meacháin,' with roots in Irish Gaelic. The prefix 'Ó' (descendant of) was dropped in Anglicization, making 'Meacháin' become 'Meehan' in English-speaking contexts.
Meehan carries Irish heritage in its vowel sounds—that 'ee' sound is distinctly Celtic. Surnames preserve genealogy in their very letters; an Irish person's surname is a linguistic time capsule of their family's history and geography.
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