Use 'puny' to express physical smallness or lack of strength, often with a dismissive tone. Even with his puny arms, he managed to lift the box.
Pro Tip 2/3
Underestimation
When calling something 'puny', it suggests that it's too small or weak to be effective or valuable. Despite their puny size, ants can carry objects many times their weight.
Pro Tip 3/3
Descriptive Scale
'Puny' is relative; what is puny to one may not be to another. Context is key. To a giant, the large boulder was merely a puny stone.