To make something worse.
To combine in a confused fashion; to mingle so as to make the parts indistinguishable.
To stun or amaze.
To cause to be ashamed; to abash.
To defeat, to frustrate, to thwart.
To fail to see the difference; to mix up; to confuse right and wrong.
To perplex or puzzle.
A confounding variable.
To make things worse for someone who is going through a difficult time.