The definition is relatively straightforward. It means to orgasm without using your hands (or somebody else's). Not that hard to do honestly.
John got a hands free orgasm (HFO) from that lady across the street, or more specifically, he got head and busted his load.

Sarah gave his man a hands free orgasm by using her feet.

Really, there are endless ways of orgasming without the utilization of the metacarpus. Humping is one of 'em.
by Mary Mary Quite The Contrarian December 24, 2021
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Awaking while having an orgasm to find your hands no where near your genitals.
Mike: It's the middle of the night, Carrie, what's going on?

Carrie: Wow! I guess my hands free orgasm woke us both up.
by LinShady October 27, 2014
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