Definition of: kelp

(kelp) noun
1. Any large coarse seaweed (family Laminariaceae); specifically, the California sea palm (Postelsia palmaeformis).
2. The ashes of seaweeds: formerly the source of soda as used in glassmakmg and soapmaking, now a source chiefly of iodine.
—giant kelp A very large, tough, and massive seaweed (Macrocystis pyrifera), belonging to the brown algae: it is found mainly on the Pacific coast of the United States, and has been known to reach a length of 700 feet. [ME culp; origin uncertain]