Turn the palm facing down

• Rotate as an extremity
• Rotate the hand, in a way
• Rotate down, as one's palm
• Rotate inward while walking, as one's foot
• Turn down, as one's palm

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Pronate \Pro"nate\, a. [L. pronatus, p. p. of pronare to bend forward. See Prone.] Somewhat prone; inclined; as, pronate trees. --Kane.

WordNet Word definitions in WordNet
v. turn the forearm or the hand so that the palm is directed downwards

Wiktionary Word definitions in Wiktionary
Somewhat prone; inclined. v 1 (context transitive anatomy English) To turn or rotate one’s hand and forearm so that the palm faces down if the forearm is horizontal, back if the arm is pointing down, or forward if the forearm is pointing up; to twist the ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
1848 (adj.); 1819 (v.), from Late Latin pronatus , past participle of pronare "to bend forward," from pronus "prone" (see prone ). Related: Pronated ; pronating .