An uninhabited island, especially one in the tropics(noun)
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Use "desert island" in a sentence
"If you've read Robinson Crusoe you may recall a passage where he weighs up his plight on the desert island like a book-keeper, evil on one side, good on t'other."
"In the intervals of wringing out hot flannels for her quinsy she would amuse herself by devising a desert island expedition, on a larger and possibly a damper scale than hitherto, against the time when she should be out again."
"As soon as the winds shifted from west to east, Nearchus weighed anchor and sailed along the coast to a desert island called Domai, where his men searched in vain for water."