CEDICT
to become incumbent upon, one's turn to do something (e.g. now it's (your) turn)
Wiktionary
指在一個序列中的人、事、物到了可以執行或被執行動作的時間點。
維基詞典
It's Ziri's turn.
Source: Tatoeba
It's your turn.
It's now my turn.
Whose turn is it?