an act of breaking or failing to observe a law, agreement, or code of conduct

a breach of confidence

they alleged breach of copyright

a gap in a wall, barrier, or defence, especially one made by an attacking army

a breach in the mountain wall

make a gap in and break through (a wall, barrier, or defence)

the river breached its bank

(of a whale) rise and break through the surface of the water

we saw whales breaching in the distance