Definition of Plimsoll line in US English:

Plimsoll line

(also Plimsoll mark)


  • A marking on a ship's side showing the limit of submersion legal under various conditions.

    • ‘Below this a single Plimsoll mark, ‘VI ‘, showing the draft of the tug in feet.’’
    • ‘Belisha beacons, bobbies on the beat, Big Ben, a ship's Plimsoll line - all are familiar terms with their origins in the names of notable MPs of their age.’
    • ‘It does not have a Plimsoll line like a cargo vessel.’
    • ‘In the nineteenth century, Plimsoll was credited with naming the Plimsoll line, a line that shows the depth to which a properly loaded ship can be immersed in water without sinking.’
    • ‘Life-jackets, boats, signals, Plimsoll line, radio, all made navigation safer.’


Named after Samuel Plimsoll (1824–98), the English politician whose agitation in the 1870s resulted in the Merchant Shipping Act of 1876, ending the practice of sending to sea overloaded and heavily insured old ships, from which the owners profited if they sank.