There is a rising number of visitors to Benefits of Honey writing to me and asking this question. Unfortunately, I don't really have a clear answer to this, but would like to share my experience and thoughts about this issue from a honey consumer perspective.
The term "adulterated honey" implies that the honey has been added glucose, dextrose, molasses, corn syrup, sugar syrup, invert sugar, flour, starch, or any other similar product, other than the floral nectar gathered, processed, and stored in the comb by honey bees. Legal standards and requirements for foods, including honey quality, and tests for honey adulteration vary widely amongst countries and some may not meet the wish of every consumer around the world.
Buying Pure Honey
Personally, when selecting honey in the shop, I think it's almost impossible to tell the bad from the good by just looking at the honey content through the jar or studying its food and nutrition labels, unless you perform honey purity tests like explained here. My take is always -- go for the trusted or better known brands. The best is to be able to ask the source or supplier of the honey questions about the honey origin and how the honey is harvested and processed to get an assurance on the quality. However, this is not always possible when we do not have direct access to bee farms and beekeepers.
For commercial honey, we all know that a "pure honey" label doesn't guarantee at all that it is not diluted with water and further sweetened with corn syrup; it just promises that there is real pure honey inside, with no suggestion of its amount. The law does not require a "pure honey" label to say how much pure honey is in the bottle