The word "unseeyn" is a unique and somewhat archaic spelling of the more commonly seen word "unseen". The pronunciation of this word is /ʌnˈsiːn/, with the first syllable as "un" to signify negation or opposite, and the second syllable as "seen", which refers to something that has not been observed or noticed. This spelling is not commonly used in modern writing but can sometimes be found in literature from earlier time periods.