The poison apple is simply called "the poison apple" in most interpretations of the Snow White story.
There is no specific name given to the apple in the original Grimm's Fairy Tale, nor in Disney's adaptation. However, the apple is often associated with the Evil Queen's evil intentions and the danger it represents.
It is worth noting that the apple in the story is not necessarily a specific type of apple. It is simply a symbol of temptation and death, and its appearance and name can vary depending on the interpretation.