1. A marvel of industrial engineering, linking the industrial town of Hull with the fishing port of Grimsby

2. The female perineum, so called because like the Humber Bridge it links a place that stinks of shit with one that stinks of fish.

the fleshy section in between a woman's vagina and anus, also known as a female gooch. So-called because the Humber Bridge in England links the towns of Hull & Grimsby, i.e. 'the fishy bit to the shitty bit'.