expression, ichidan verb
make someone let their guard down; lull someone into a false sense of security
Causative form of 油断する, used when someone or something causes another person to become careless or off guard.
彼の優しい言葉が私を油断させた。
His kind words made me let my guard down.
相手を油断させる作戦だ。
It's a strategy to make the opponent drop their guard.