Cartel-ship
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
A vessel commissioned in time of war to exchange the prisoners of any two hostile powers; also to carry any particular proposal from one to another. For this reason, the officer who commands her is particularly ordered to carry no cargo, ammunition, or implements of war, except a single gun for the Purpose of signals.
Crawford v. The William 'enn, 6 Fed. Cas. 778.