Webster’s Revised Unabridged Dictionary · 1913
Plimsoll's mark
Plim′soll's mark′ (plĭm′sŏlz märk′). (Naut.) 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.