What does "seno" mean?

发音：se~no 来自日语的せーのっ，用作多人协同进行同一个行动前的指令，相当于中文的“预备起”或是“三二一”。在国内主要被用在给日系偶像喊call前的发令。

ENPronunciation: se~no. From the Japanese 'せーのっ', used as a command before multiple people perform the same action together, equivalent to the Chinese 'yùbèi qǐ' (ready, set, go) or 'sān èr yī' (three, two, one). In China, it is mainly used as a command before shouting calls for Japanese idols.