Prohibited or excluded by proclamation, law, or treaty.n. Illegal or prohibited traffic.n. Anything by law prohibited to be imported or exported.n. In the United States, during the civil war, a negro slave, especially an escaped or a captured slave: so called from a decision of General B. F. Butler, in 1861, that slaves coming into his lines or captured were contraband of war, and so subject to confiscation.To declare prohibited; forbid.To import illegally, as prohibited goods; smuggle.