Longman Dictionary of Contemporary English - convoy

~1 n 1 a group of vehicles or ships travelling together  (A convoy of lorries arrived bringing supplies of food and medicine. | in convoy)  (We decided to travel in convoy so that no-one could lose their way.) 2 a group of armed vehicles or ships whose purpose is to travel with others in order to protect them  (They were escorted through the danger area by a naval convoy. | under convoy (=protected by a convoy))  (The weapons were sent under convoy.) ~2 v to travel with something in order to protect it  (Battleships helped to convoy much-needed supplies to Britain in 1917.)