end of the arm; forearm area; wrist and hand area
Refers to the lower part of the arm, roughly from the elbow to the fingertips. Not a highly technical anatomical term; used in everyday contexts.
My lower arms get cold and go numb.
Move from the shoulder, not just from the forearm.
Compound of 腕 (ude, 'arm') and 先 (saki, 'tip' or 'end'). The reading うでさき follows standard rendaku voicing rules.