A masturbation technique in which a man rips the wings off of a fly, takes a bath and places the wingless fly on the head of his erect penis. The masturbater allows the fly to walk over the tip of the erect penis (like a castaway on a desert island) until the man ejaculates.
Hey Dennis, can you catch me a fly... I think I want to take a Desert Island after dinner.
"Hey Ozzy Osbourne, what ten British albums would you take to a desert island?"
"Revolver, Sgt. Pepper's Lonely Hearts Club Band, Band on the Run, So, Dark Side of the Moon, Abbey Road, Imagine, Blizzard of Ozz, Led Zeppelin, and Machine Head."
When a woman is so sexually charged she treats a man's penis with an extreme amount of attention for a prolonged period during any particular sex session. The reference is that she's acting like it might be the only penis she has seen, or may see, for a considerable amount of time; i.e., like she's on a deserted island and just found it.
A relationship that would be perfect if the two of you were alone on a desert island, but that doesn't work in the context of your lives outside of each other