n (nautical) On a wooden
mast, a circular disc (or sometimes a rectangle) of wood near or at the top of the mast, usually with holes or
sheaves to
reeve signal
halyards; also a temporary or emergency place for a
lookout. "Main" refers to the
mainmast, whereas a
truck on another mast may be called (on the mizzenmast, for example) "mizzen-truck".