"to stop or check the flow of (blood or tears, for example); to stop the flow of blood from (a wound)" — American Heritage Dictionary
"see staunch" — Webster's New World College Dictionary
Funny how being reared on style guides can mess you up for life. I long took the Associated Press Stylebook's words as gospel:
But both Webster's New World and American Heritage allow "staunch" as a verb and a synonym of "stanch." In fairness, I should note that WNW also adds:
"stanch, staunch: Stanch is a verb: He stanched the flow of blood. Staunch is an adjective: She is a staunch supporter of equality." (AP)
"USAGE—For the adj., staunch is now the prevailing form in the U.S.; for the v., usage is about evenly divided between staunch and stanch"
Still, AP should have used imperatives (Use "stanch" as a verb) instead of absolutes (Stanch IS a verb).