1.
fuse; match; priming fire
Originally, the small fire used to ignite a cannon or firearm. The literal ignition source.
大砲の口火を切る。
To light the fuse of a cannon.
2.
opening shot; trigger; spark that starts something
Figuratively, the initial action or remark that triggers a larger event, discussion, or movement.
議論の口火を切った。
He opened the discussion.
その事件が口火となって、全国的な抗議運動が始まった。
That incident was the spark that started a nationwide protest movement.
彼女が口火を切ったことで、他の社員も不満を口にし始めた。
After she spoke up first, other employees also began voicing their complaints.
Almost always used in the set phrase 口火を切る (to cut the fuse → to be the first to speak/act, to kick things off). The literal meaning (sense 1) is now rare; the figurative sense dominates modern usage. Composed of 口 (mouth/opening) + 火 (fire).
COMMON PATTERNS:
- 口火を切る: to open (a discussion); to fire the first shot; to be the first to act
- 口火となる: to serve as the trigger/spark for something
SIMILAR WORDS:
- 皮切り: the start; the beginning — similar to 口火 but more neutral; often used in ～を皮切りに (starting with...)
- きっかけ: trigger; catalyst — the most common neutral word for what prompts something to happen
- 発端: origin; beginning — focuses on the starting point of a series of events
- 導火線: fuse (literal) — the actual physical fuse of explosives; also used figuratively