
A small, pellet-filled round bag used for a variety of games where players must keep the bag off the ground using their feet and other parts of the body excluding hands.
that hacky sack thing where you know like you're bending your knee upwards. You know what I mean?
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"The speakers use 'hacky sack' as a specific reference to a leg-checking technique in MMA, comparing the physical movement to the act of playing with a hacky sack."