A mark conspicuously painted on the port side of all
British sea-going merchant vessels, to indicate the limit of
submergence allowed by law; -- so called from Samuel Plimsoll, by whose
efforts the act of Parliament to prevent overloading was procured.
* These videos are coming directly from Youtube, they may or may not be most relevant to the word "Plimsoll's mark"
What is Define Dictionary Meaning?
Best thing is, its free and you can even contribute without creating an account.