Why is an arrow always called poisonous in different types of media (games, movies, etc.) when by definition that would not be true.
Venom is delivered by a sting, bite, etc. and is injected into the target while poison needs to be absorbed or ingested for it to take effect. See this nice article from the Australian Academy of Science.
Following that logic, an arrow would be considered venomous as it needs to pierce the target in order to deliver the toxin. It does absolutely nothing if you simply touch it.