Blooding refers to the act of a novice Yautja being ritually marked with the acid blood of their first Xenomorph kill. Blooding is different for each Clan or Tribe. In "ALIENS VS PREDATOR", the 2004 movie, an unblooded Yautja kneels as they use the Xenomorph's blood (presumably a body part, as the unblooded Yautja forementioned used a Facehugger's finger) to mark themselves with their clan symbol. This could show the diversity in rituals, considering there are multiple Clans of Yautja.