Entry 1 sense Webster, 1913 Invader /ĭnˌ-vād'-ẽr/ · In·vad·er · IPA /ɪnˈveɪ.də(ɹ)/ 01 n. One who invades; an assailant; an encroacher; an intruder. 1. One who invades; an assailant; an encroacher; an intruder.