Entry 1 sense Webster, 1913 Assassination /əs-ăsˌ-ən-āsh'-ən/ · As·sas·si·na·tion · IPA /əˌsæs.ɪˈneɪ.ʃən/ 01 n. The act of assassinating; a killing by treacherous violence. 1. The act of assassinating; a killing by treacherous violence.