You won’t find this in any modern dictionary except the largest, as it has quite gone out of use except when speaking of historical matters. The word meant a cow pasture, not some peasant’s patch where one cow was kept for her milk, but larger-scale pasturage where cattle were kept and bred and as a source of working oxen.
The word is usually linked to grazing land in the moors and valleys of the Pennines in Yorkshire and Lancashire. In the thirteenth century numbers of vaccaries were carved out of the old private hunting chases of the nobility, who created them in an attempt to get some revenue back from their holdings. Vaccaries were small-scale commercial cattle farms — in places, as around Pendle (more famous for its witches), you can still see the big stone-slab walls that kept the cattle enclosed.
The word comes from the mediaeval Latin vaccaria, derived from vacca, a cow. Vaccinate is closely linked, since that derives from the Latin vaccinus, of or from a cow, as cow-pox serum was used to protect people against smallpox.