What is broaching

[Rusty Barrels]

Is that when a large wave pushes a boat end over end, or swings the stern to the side and is hit on the port or starboard side by a large wave.

[callenish gunner]

this defines it pretty well:

wikipedia

[Captain Jim]

A good definition of broaching, to be sure, but an end-over-end capsize is called "pitchpoling" and makes a normal broaching look like a walk in the park.

In a broach the boat will usually right itself after the wind is spilled from the sails unless a large wave drives the boat's mast underwater, perhaps all the way through 360 degrees for a complete rollover. Still, a well-found vessel may survive such treatment. Just hold on tight and pray that (1) the rig stays together and (2) that it doesn't stop halfway and "turtle" the boat.

A pitchpole is always accompanied by a large wave taking the ship from astern and driving the bow into the water and taking the stern over the top. The forces generated almost always remove the rig, and usually destroy the boat.