To Be Smashed
To Be Shattered, To Break
intransitive verb, ichidan verb
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb.
This is an intransitive verb, so this verb means to be smashed, to be shattered, or to break (for things like waves and tension!).
Since this word has okurigana (hiragana attached to the kanji) you know that it's probably going to be the kun'yomi reading.
Lucky for you, the kanji readings for transitive and intransitive verbs are almost always the same. Once you learn one, you know them both! This reading is the same as 砕く.
Suddenly, the window shattered into tiny pieces.
I like sitting on the beach and watching the waves break on the shore..
When I felt like the tension in the air finally broke, the party was almost over.