The joy of owning an Apple product is so great, the owner or potential owner will emit a moan of pleasure and, depending on the owner's gender, will sometimes have a hard-on.
Immediately after having an applegasm, the eater's face will be covered with an empty mind, zombie-like grin.
Applegasms are most common after owners or potential owners stand in line for hours or days while waiting for the next great product.
Dude, you got the new Apple! you look like you just had an Applegasm.