1.
one shot, one blow
A single shot (gun), punch, or strike.
一発殴った。
I punched him once.
銃を一発撃った。
I fired one shot.
花火を一発打ち上げた。
We launched one firework.
2.
one try, in one attempt
Doing or achieving something in a single attempt.
一発で合格した。
I passed on the first try.
一発勝負だ。
It's do or die.
一発で決めたい。
I want to nail it on the first try.
3.
big hit, jackpot
A single decisive success, especially in gambling or sudden fortune.
一発逆転を狙う。
I'm aiming for a come-from-behind victory.
一発当てて金持ちになりたい。
I want to hit it big and get rich.
一発屋を狙うのは危険だ。
Going for a one-hit wonder is risky.
一発 relates to single actions with impact.
PHYSICAL ACTION (Sense 1):
- 一発殴る: to punch once
- 一発撃つ: to fire one shot
- 一発かます: to land a blow (slang)
SINGLE ATTEMPT (Sense 2):
- 一発で: on the first try
- 一発勝負: do-or-die situation
- 一発合格: passing on the first try
BIG SUCCESS (Sense 3):
- 一発逆転: dramatic comeback
- 一発当てる: to hit it big
- 一発屋: one-hit wonder
MAHJONG:
- 一発: a bonus for winning within one turn after riichi