1.
all at once; simultaneously; in unison
Describes multiple people or things acting at the same time in a coordinated or synchronized manner.
生徒たちが一斉に立ち上がった。
The students all stood up at once.
合図とともに一斉にスタートした。
They all started simultaneously at the signal.
桜の花が一斉に咲き始めると、公園は大勢の花見客でにぎわう。
When the cherry blossoms all start blooming at once, the park bustles with crowds of flower-viewing visitors.
USAGE:
一斉に emphasizes that an action happens simultaneously across a group. The noun form 一斉 can also be used as a prefix: 一斉検査 (simultaneous inspection), 一斉送信 (mass sending/broadcast).
COMMON COLLOCATIONS:
- 一斉に立ち上がる (to stand up all at once)
- 一斉に始まる (to begin simultaneously)
- 一斉に咲く (to bloom all at once)
- 一斉検挙 (mass arrest)
NUANCE:
Compared to 同時に, which simply means "at the same time," 一斉に implies a larger group acting together and often carries a more dramatic or striking impression.