爆弾
ばくだん · bakudan · JLPT N1 · noun
bomb
💣 爆 burst + 弾 bullet = bakudan: a bullet that bursts, which is a bomb
Bakudan is built from 爆 (burst, explode) and 弾 (bullet, shot, shell). The same 爆 starts 爆発 (bakuhatsu, explosion), and 弾 appears in 弾丸 (dangan, bullet).
爆 — fire 火 + 暴 (violent/sudden, phonetic)
A semantic-phonetic compound: 火 (fire) gives the meaning, while 暴 (sudden, violent) supplies the sound and reinforces the sense. Originally meant to burst or explode with fire, later extended to any sudden, forceful eruption like popping or bursting.