An archaic or rare adjective meaning somewhat eerie or having qualities that inspire unease or fear.
From eerie plus the suffix -some (meaning 'characterized by' or 'full of'), following the pattern of words like fearsome, awesome, and handsome. Rarely used in modern English.
Eerisome belongs to an old family of words—fearsome, awesome, lonesome—that English speakers used before we started using -y adjectives like spooky and creepy.
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