The position of the sword hand when the palm is facing up.(noun)
The action of rotating the forearm so that the palm of the hand is turned up or forward.(noun)
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Use "supination" in a sentence
"Rest the forearm on a table, with the palm up (an attitude called supination)."
"I won't drag you through a turgid technical history of the sneaker including waffles, bubbles, air cushioning, antipronation, supination, orthotics and barefoot technology."
"Your current shoes may show the telltale signs of overpronation (too much inward rolling of the foot) or excessive supination (too much outward rolling), so bring them along for the salesperson to examine."