1A sign, signal, or cue — a gesture, sound, or call used to convey timing or intent, prompting someone to start something or letting them know something.
彼は手を振って合図した。
He waved his hand as a signal.
先生の合図で授業が始まった。
The lesson began at the teacher's cue.
信号が青に変わるのが渡る合図だ。
The light turning green is the signal to cross.
二人は目で合図を交わしてから演奏を始めた。
The two exchanged a glance as a cue, then began playing.