1.NounA deserted island, an uninhabited island, especially one in the tropics and a small and almost entirely sandy desert.
"What would I take with me to a desert island?"
2.NounAn island that is completely or mostly a desert, an arid island.
"Why are you marooning me on a desert island? It's probably full of guano. Can't I go somewhere nice?"
3.NounDescribing a thing considered so personally indispensable or beloved that one could never tire of it, used especially for books and music.
"No, no, no. It's a thought experiment. Your desert island books are the one or five or ten books that you could always learn from and never get sick of."