overarm vs overhand

overarm and overhand both are adjectives.

Word	Noun	Adjective	Verb	Adverb
overarm	No	Yes	No	No
overhand	No	Yes	No	No

As adjectives, overarm and overhand are synonyms defined as:

overarm and overhand: with hand brought forward and down from above shoulder level

Other synonyms of overarm include overhanded.

overarm (adjective)	overhand (adjective)
with hand brought forward and down from above shoulder level	with hand brought forward and down from above shoulder level
	sewn together with overhand stitches (close vertical stitches that pass over and draw the two edges together)