Not dating anyone, not attached to anyone, not interested in anyone.
First coined by Shakespeare.
That girl has no interest in any of the boys at school. She'll probably be fancy free until she gets to college.
The act of a large, naked fat man girating his hips rapidly in a sexually suggestive fashion to make his limp Piggly Wiggly
Fancy free can also indicate that said fat naked man gaily dances through fields of flowers with his arms above his head and flapping his hands rapidly like a bird in flight, just like a pretty ballerina
"Would you ever beeeeeeeeeee so FANCY FREEEEE to let your naked Pee pee Swing in the morning Breeeeeeeeeezeeeee!"