後あと出だしジャンケン

Meanings

waiting to see opponent's move in rock-paper-scissors; playing a waiting game

Literally 'delayed-throw rock-paper-scissors'; cheating by throwing after seeing the opponent's hand. Figuratively, waiting to act until the other side's move is clear, often in negotiations or strategy.

Kanji

後behind, back, later
出exit, leave, go out

Related words

後あと出だし
後出し alone means 'delayed throw' or 'waiting to see the opponent's move', often used in the same figurative sense. 後出しジャンケン specifies the rock-paper-scissors context.
じゃんけん
じゃんけん is the standard word for rock-paper-scissors. 後出しジャンケン is a compound describing a cheating tactic within that game.

Written forms

後あと出だしジャンケン
Standard kanji-katakana spelling. ジャンケン is commonly written in katakana.
後あとだしジャンケン
Variant with だし in hiragana; less common but seen.

Etymology

Compound of 後出し (あとだし, 'delayed throw') and ジャンケン ('rock-paper-scissors'). The exact origin is uncertain, but it likely emerged as a colloquial term for the cheating tactic.