Keelhaul

Verb - punish someone by dragging them through the water under the keel of a ship, either across the width or from bow to stern.

Origin - From the Dutch kielhalen.

"Arrrr, walk the plank before I keelhaul you, you scurvy, landlubber's dog. I've got t' get back to me bottle of rum and me pieces of eight in the dead man's chest." Every time he opened his mouth, peg-leg, hook-hand, one eye Captain Pete the pirate would try, and fail, to not embody the much-ridiculed pirate stereotype.

This word makes the list because it is impossible to pronounce without adopting a typical pirate accent. Cue many an "Arrrr" and "Ya filthy landlubber!" from myself and hopefully many readers. I like the way the definition specifies that it can be done lengthways or widthways, just in case there could be some sort of confusion.
Unfortunately, the meaning isn't very pleasant but then again, neither were real pirates, despite what Disney would have you believe. Yet more unfortunate is how difficult it is to work the word into a conversation, unlike some others in this blog. Unless of course you have recently keelhauled someone (hopefully not, I'm pretty sure it's illegal) or are at a fancy dress party, dressed as a pirate (it doesn't work at a James Bond party, I've tried). Perhaps it's a word to unleash when no-one is around. Everyone has an inner pirate so try releasing yours by saying this word as often as possible.