In a state of thrilling excitement or suspense; thrilled or excited through and through.
From a- (prefix meaning 'in' or 'on') plus thrill. This is an archaic or poetic form that emphasizes the intensity of being filled with thrill.
Athrill is the kind of Victorian word that modern writers use to sound dramatic—it appears in old novels to describe characters in heightened emotional states, and it's one of those a- prefix words that sound more intense than the base word.
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