In mahjong, a 'safe tile' that can be discarded without risking giving an opponent a winning hand (often abbreviated as 'anpai').
相手がリーチしたら、リーチ者にとって安牌と思われる牌を捨てる。
When an opponent declares riichi, discard a tile that appears to be safe for them.
その牌は場に多く出ているので今は安牌だ。
That tile has appeared many times on the table, so it's safe to discard now.
Figuratively, a 'no-risk choice' or an 'easy-to-handle person' — someone or something considered safe and uncontroversial.
今回は波風立てたくないから、安牌を選んでおこう。
I don't want any trouble this time, so I'll choose the safe option.
彼は会議ではいつも安牌だから、意見が変わらない。
He's always a safe bet in meetings, so his opinion never changes.