(verb)
to pierce something or make a hole in it, typically in order to remove and use its contents;
e.g. They decided to broach a bottle of champagne and make a toast to the occasion.
(verb)
to rise upwards through water and break its surface from below, used to describe the behavior of animals such as sea mammals and fish;
e.g. We saw a whale broach at some distance from our boat.
(noun)
some tapered or pointed tool used for a particular purpose, such as a tool used to pierce/tap casks, a rod on which meat is roasted, or a tool used to cut and shape plastic or metal;
e.g. He used a broach to open up the cask of ale.
(verb)
in nautical usage, to dangerously veer or be tossed forward such that one side of the vessel is towards the waves (or the wind), often resulting in a loss of steering control;
e.g. The storm caused the ship to broach to and fro among the waves.