Entry 1 sense Webster, 1913 Expeditionary /ĕkˌ-spəd-ĭsh'-ən-ĕrˌ-ē/ · Ex·pe·di·tion·a·ry · IPA /ˌɛkspədˈɪʃənˌɛriː/ 01 a. Of or pertaining to an expedition; as, an expeditionary force. 1. Of or pertaining to an expedition; as, an expeditionary force.