Pretty obvious meaning. "Straight Line" is the harpoon shot. From "Feel it burst," to "Physeter Catodon," the song speaks of the killing and harvesting of the whale. Phsyeter Catodon is actually the scientific name of the sperm whale, which was the breed of whale Moby Dick was. "Culture Vulture, Elephant Graveyard, Culture Vulture," is about how the carcass will grow cultures of bacteria and attract scavengers, like vultures. Elephant Graveyard is obviously alluding to the number of whales Ahab had killed. The last three lines, "Wreaking Vengeance, Assault with all martial rage, sail on," are about Ahab's hunt (mission) to find the white whale and bring it down, thus achieving retribution. Because the whale killed in the song is not the white whale, Ahab commands his men to sail on.