The second mast, or that which is next above the lower mast, and below the topgallant mast.

The second mast, or that which is next above the lower mast. Above that is the top-gallant-mast.

The spar next above a lower mast and below the topgallant mast.

the mast next above a lower mast and topmost in a fore-and-aft rig

a smaller mast fitted on top of a heavier lower mast to fly more sail

The spar above the lowermast, but below the topgallant mast. LISSA’s foremast and mainmast have three sections: lowermast, topmast, and topgallant mast. Her mizzenmast has two sections: lowermast and topmast.

mast on top of another mast.

a second spar carried at the top of the fore or main mast, used to fly more sail.

The masts of traditional sailing ships were not single spars, but were constructed of separate sections or masts, each with its own rigging. The topmast is one of these.