A.T. Robertson Commentary Luke 21:15

"for I will give you a mouth and wisdom, which all your adversaries shall not be able to withstand or to gainsay." — Luke 21:15 (ASV)

Your adversaries (ο αντικειμενο υμιν). Those who stand against, line up face to face with (note αντι-).

To withstand or to gainsay (αντιστηνα η αντειπειν). Two second aorist active infinitives with αντι- in composition again. But these "antis" will go down before the power of Christ.