'Bitter' in the Bible

The name of the star is 'Wormwood;' and a third part of the waters were turned into wormwood, and vast numbers of the people died from drinking the water, because it had become bitter.

So I went to the angel and asked him to give me the little book. "Take it," he said, "and eat the whole of it. You will find it bitter when you have eaten it, although in your mouth it will taste as sweet as honey."

So I took the roll out of the angel's hand and ate the whole of it; and in my mouth it was as sweet as honey, but when I had eaten it I found it very bitter.