An exclamation of surprise or shock, usually preceded by "holy."
This is used in reference to the webcomic Lumia's Kingdom, in which a character uses it.
It takes him exactly three hours and forty-seven minutes to detect anything out of the ordinary, to which he will always respond 'Holy Megapode!'
Really big herd or school of marine animals (zool.)
Dozens and dozens of dolphins, all leaping and diving their way to new feeding grounds are a megapod.