What kind of cactus is this?

Question:I have a tall thin green speckled colored smooth plant that has a triangular stem-center. It has thick hard thorns growing on all three points of its triangular center. The base of the plant is hard and brown. Green leaves grow out beside the thorns. Its cutlings ooze tons of white stuff when cut. The plant is now taller than me. I know it isn't a regular cactus, but I can't figure out what it is. Does anyone know?

Answers:
It's not a cactus , but a Euphorbia . The milky white sap gives it away, if nothing else . Which exact species- ? Cactus topiaries , esp. the neon-colored varieties, that can't survive on their own , are grafted onto Euphorbia. This is probably the species you have . Btw Poinsettias are Euphorbias