What does 'Civil blood' mean in Romeo and Juliet?

Answer 1

"Two households, both alike in dignity

In fair Verona where we lay our scene,

From ancient grudge break to new mutiny

Where civil blood makes civil hands unclean."

The word "civil" means "from the city" (Latin civitate), as in "civil servant". It can also mean polite or well-behaved, as "keep a civil tongue in your head." Using the first meaning, the phrase is quite literal, where the blood of the city (or rather the blood of the people of the city) makes their hands dirty. But there is also a play on the second meaning, so that the phrase can also be taken to mean, where the blood of the people of the city makes their well-behaved hands dirty--in other words, their good behaviour is tarnished with their blood.