Yes, jellyfish can be considered poisonous because they inject venom into their victims through stingers.
Jellyfish stings involve thousands of very tiny stingers called nematocysts that remain in the skin. These nematocysts can continue to release (or "fire") jellyfish venom (poison) into the body after the initial sting. Treatment varies based on the type of jellyfish, but rinsing with vinegar is often recommended.
