Entry 1 sense Webster, 1913 Deductive /dĭd-ŭk'-təv/ · De·duct·ive · IPA /dɪˈdʌktɪv/ 01 a. Of or pertaining to deduction; capable of being deduced from premises; deducible. 1. Of or pertaining to deduction; capable of being deduced from premises; deducible. “All knowledge of causes is deductive.” — Glanvill. “Notions and ideas . . . used in a deductive process.” — Whewell.