The answer for upper limb is almost always "arm." Was the clue plural?
Arm
Here are a couple: diet, dime, lime, time, fine, and limb.
what is the three letter word for limb used for walking
orthosis
A 'forelimb'.
An arm or a leg are three letter words for limbs.
limb, twig
A five letter word for the opposite of lower is upper.
Brachi is the word used for something that relates to the upper limb. For example the proper name for the muscle commonly reffered to as the Bicep in the arm is Biceps Brachi. Another example is the brachial plexus which is the complex arrangement of nerves that supple the upper limb.
A four letter word starting with the letter a is able.
Lard is a four letter word for grease.
That Four-Letter Word was created in 2006.
A four letter word for 'in addition to' is also.