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.
虚弱な子供を見ると、心配になります。
Whenever I see a weak child, I get worried.
私の息子は生まれつき虚弱体質で、運動はできません。
My son was born with a weak constitution, so he can’t exercise.
私は胃腸が虚弱なんです。
I have a weak stomach.