Impossible
Unreasonable, Overdoing
noun, verbal noun, な adjective
If you can do nothing within reason, then what you're trying to do is unreasonable and probably downright impossible. If you still try, you're probably just overdoing it.
This is a jukugo word, which usually means on'yomi readings from the kanji. As long as you know the readings for these kanji, you should be able to read this word just fine.
ゼッタイ無理です。
It is absolutely impossible.
あんまり無理なことばかり言わないでください。
Please don't be too unreasonable.
無理しすぎないで、自分の体も大事にしてね。
Don't overdo it. Take care of yourself, too.