Entry 1 sense Webster, 1913 Probably /präb'-əb-lēˌ/ · Prob·a·bly · IPA /ˈpɹɑ.bə.bli/ 01 adv. In a probable manner; in likelihood. 1. In a probable manner; in likelihood. “Distinguish between what may possibly and what will probably be done.” — L'Estrange.