Overarm is how you throw — or bowl, or swim — when the arm goes up high, above the shoulder, and comes over the top. In cricket, an overarm bowl is the usual one; an underarm bowl keeps the arm down by the body, and that feels like a different game. Netball and some playground games use the same contrast. It can describe the throw (an overarm throw) or the way you do it (to throw overarm). It is a sports word, not a fancy one. Though actually, if you pick up American sports writing, you will more often see overhand for the same high-arm action; overarm is the word many British and learner dictionaries prefer. It is not a medical word about the arm itself, and it is not two separate words meaning “above the arm”.

上手；過肩（投球）。手臂高過肩膀、從上方出去。美式英語較常說 overhand；台灣棒球會說「過肩投球」或「上手」。