Nematocyst

noun

1. A capsule within specialized cells in the tentacles of cnidarians, such as jellyfish and corals, containing a barbed, threadlike tube that delivers a toxic sting to predators and prey.
2. A thread-cell or lasso-cell; a cnidocell or cnida; one of the organs of offense and defense peculiar to cœlenterates, as jellyfishes, by means of which they sting. See cuts under cnida, Actinozoa, and Willsia.
3. A lasso cell, or thread cell. See lasso cell, under lasso.
4. A capsule, in certain cnidarians, containing a barbed, threadlike tube that delivers a paralyzing sting