Weak
Feeble, Weakness, Feebleness
noun, な adjective, の adjective
You have yourself a void of weakness. This means you are weak and feeble.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
私は生前、虚弱すぎてベッドから出られなかったんです。
I was too frail to get out of bed before I died.
私の弟は生まれつき虚弱で、運動はできません。
My little brother was born frail and unable to exercise.
マスク生活で何年も外気にさらされなかったせいで、気道が虚弱になってるのかもしれません。
Maybe my airways are frail because I haven't been exposed to the outside air for years due to living in a mask.