To stand firm
As an adjective, staunch means firm. You might want to go to that concert Friday night, but your parents’ staunch opposition prevents you.
Staunch is sometimes used as a verb to mean “to stop the flow of a liquid,” but most usage books will tell you it’s better to use the word stanch for the verb. Think of a soldier stopping and standing still, and you will understand the connection between the two meanings. The adjectival form should make you think of “stand,” as in “stand firm,” or “take a stand.” It comes from the French estanche meaning “watertight” and the Latin stanticare, which is probably from stans for “stand.”