打暗号 meaning in Chinese

[方言] give a secret signal

The road became narrower and narrower so i decided to stop the taxi after explaining to them the difficulty in continuing . there was total silence , then the person sitting in front signaled several times to the others in the back seat . one man from the back stepped out and came to my side
路越来越窄，我不准备再往前走，我说明理由之后将车停下来，这时车中一片沈寂，前座的人打暗号给后面的人，喊了好几声，后排的人便下来到我座位旁，抽出刀子抵住我的右胸，车上其馀的人也拿出刀来威胁，也许是师父的加持，我竟然一点也不慌张，拿出钱给他们，四人犹豫一阵子后决定放我走。