One who is not from the local planet/world/plane/dimension/universe.(noun)
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Use "off-worlder" in a sentence
"His off-worlder clothing — closefit pants, shirt and vest, laced boots — did little to mask the hard, lean contours of his body."
"Liz, however, was immune thanks to her unique physiology—a few gifts passed down from an off-worlder somewhere deep in her family tree."
"Clairvoyants, mediums, shamans … The Madigan bunch, however, had the distinction of having not one off-worlder ancestor which was rare in itself, but two—a Charbydon and an Elysian."