Entry 1 sense Webster, 1913 Obsolescent /äbˌ-səl-ĕs'-ənt/ · Ob·so·les·cent · IPA /ɑbsəˈlɛsənt/ 01 a. Going out of use; becoming obsolete; passing into desuetude. 1. Going out of use; becoming obsolete; passing into desuetude.