To Pierce Into
To Stick In, To Stab Into
intransitive verb, godan 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, meaning that the piercing just happens, without emphasis on what makes it happen. That's why it means to pierce into, to stick in, or to stab into.
This is a tricky word because its English translations often end up being transitive, but in Japanese we always use this with the particle に, not を, so it's intransitive. You can see this in phrases like 言葉が心に刺さった (the words pierced my heart).
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 刺す.
言葉が刺さる
words strike a chord in one's heart
トゲが刺さる
a thorn sticks into something
矢が刺さる
an arrow pierces into something
ハリが刺さる
a needle sticks into something
目に刺さる
something pierces the eye
喉に刺さる
something pierces the throat, something gets stuck in one's throat
胸に刺さる
something goes straight to the heart, something pierces the chest
心に刺さる
something goes straight to the heart
それは心に刺さる言葉だった。
They were words that struck a chord in my heart.
矢が頭に刺さった。
An arrow embedded itself in his head.
トゲが刺さらないように気をつけてね。
Be careful not to get pricked by a thorn.