wulfhēafod-trēow, n.n: literally “wolf’s head-tree”, whatever that is. (“woolf-heh-ah-vod-treh-oh”)
This puzzling term appears in the Exeter Book’s Riddle 55. See the riddle in Old English with Franziska Wenzel’s translation and commentary on the Riddle Ages blog. Wenzel draws attention to Craig Williamson’s theory in Feast of Creatures that the wolf’s head tree is a kind of gallows, saying, “if outlaws are metaphorically called wolves, they would hang on a wolf’s head tree when they meet their deaths”.
But really, no one knows what the wulfhēafod-trēow is for certain.