1) black tide 2) oil pollution the arrival in the vicinity of the coast, carried along by the tide and floating on the water, of a large slick of crude oil or petroleum products coming either from the cargo or bunker tanks of a ship or else from the blowout of a subsea well GRM: n. (1,2) Note: black tide is a more serious amount of oil slick, oil being deposited on tidelands, causing serious industrial and ecological disaster, as in the Amoco Cadiz pollution of the Brittany coast