Noun, pl. nematocysts
1. (Biology) A capsule, in certain cnidarians, containing a barbed, threadlike tube that delivers a paralyzing sting. (wiktionary.org)
2. One of the minute stinging organelles of various coelenterates. (biology-online.org)
3. A specialized cell in the tentacles of a jellyfish or other coelenterate, containing a barbed or venomous coiled thread that can be projected in self-defense or to capture prey. (Google Dictionary)
Syn: Stinging cell.
Word origin: From nemato-, comb. form of Greek nema, nematos “thread” (genitive nematos), from stem of nein “to spin.”