sternpost

[sturn-pohst] /ˈstɜrnˌpoʊst/
noun, Nautical
1.
an upright member rising from the after end of a keel; a rudderpost or propeller post.
Also called body post.
Origin
1570-80; stern2 + post1
British Dictionary definitions for sternpost

sternpost

/ˈstɜːnˌpəʊst/
noun
1.
(nautical) the main upright timber or structure at the stern of a vessel