Entry 2 senses · 2 variants Webster, 1913 Unprobably · Un·prob·a·bly · IPA adv. adv. 01 adv. Improbably. 1. Improbably. 02 adv. In a manner not to be approved of; improperly. 1. In a manner not to be approved of; improperly.[Obs. & R.] “To diminish, by the authority of wise and knowing men, things unjustly and unprobably crept in.” — Strype.