Douglas Harper's Etymology Dictionary
"human being eaten as food," 1848, in a Pacific Islander context:\n\nBau literally stank for many days, human flesh having been cooked in every house, and the entrails thrown outside as food for pigs, or left to putrefy in the sun. The Somosomo people were fed with human flesh during their stay at Bau, they being on a visit at that time; and some of the Chiefs of other towns, when bringing their food, carried a cooked human being on one shoulder, and a pig on the other; but they always preferred the "long pig," as they call a man when baked.
["FEEJEE.
--Extract of a Letter from the Rev. John Watsford, dated Ono, October 6th, 1846." in "Wesleyan Missionary Notices," Sept. 1847]
Wiktionary
alt. human flesh used by cannibals as meat. n. human flesh used by cannibals as meat.
Usage examples of "long pig".
There would be a debate whether they should convert you to long pig or sell you to the Japanese.
This was his chance to discredit the Sorcerer and his white bitch, but if he told Malink about the man in the tree, then he would lose his chance to taste the long pig again.
The Brushwood Men probably weren't technically cannibals these days, but they weren't really human anymore, either, and it would be little consolation to their victims that the raid was for food stores and tools rather than long pig.