Frail, sickly or of a delicate constitution; weak.
"The old man looked frail and sickly as he struggled to stand up from his chair."
in a weak or feeble manner or to a minor degree
"weakly agreed to a compromise"
"wheezed weakly"
"he was weakly attracted to her"
With little strength or force.
"The old man weakly pushed against the heavy door but couldn't budge it."