Not physically strong
He was lame and of weakly health.
She sank to the bed weakly and covered her face with her hands.
The kid struggled weakly, voicing a faint cry.
Scions from a tree which is weakly, or liable to injury by frosts, are strengthened by engrafting on robust stocks.
The firelight flickered weakly; creating shadows on his face that made his expression hard to discern.