What is this ancient Greek artifact?

it is the bull symbol from minoan crete. its significance is not clear, but most likely it has to do with fertility and reproduction.

Yes it is a Minoan artifact, if it is indeed the one from the Museum of Herakleion, Crete. That one comes from Knossos. But there are more found and they are dated (for Crete) in the Neopalatial period, ca. 1700-1400 BCE. They have also been found at Mycenean sites, which might complicate the facility of the argument that such an artifact is "Greek" or not... In any case, such objects are interpreted as rhyta (plural of rhyton, ancient Greek), that is vessels for ritual libations. In general, one can very well support the suggestion that they are indeed linked to the bull-cult, which was considered of primal importance (also) in Minoan religion (for this was the case for most Bronze Age societies).

That comes from the Minoan civilization, a civililization in the island of Crete during the time 2700 B.C to 1500 B.C.

The figure is a bull, but it's to symbolize the "Bull-Leaping Fresco", a popular sport in that time/area.

Its not Greek - its Minoan; a vestige from the bull worshiping king Minos of the island of Crete.