The term 'venomous arachnid' refers to a type of arachnid that has venom, which is a toxin that can be injected into prey or predators. The most common example of this type of arachnid is the SCORPION, which has eight letters in its name. Scorpions are predatory arachnids that use their venom to paralyze and kill their prey. They are found in many parts of the world, including deserts, grasslands, and forests.