As defined by the Oregon Department of Agriculture, March 31, 2016:

Bat Guano: Definition and Characteristics:

Based on the literature reviewed and the results of laboratory analyses, the Department is revising the definition of bat guano used for product registration in Oregon, as follows:

Bat guano – is partially decomposed bat excrement. Bat guano has an organic
matter content greater than 40%, is a source of nitrogen, and may contain up to
6% available phosphate (P2O5).

As defined by the California Department of Food and Agriculture, May 11, 2017:

Notice to Fertilizing Material Licensees – Use of the term “Bat Guano” on Fertilizing Material Labels:

In order to be registered for distribution in California, products claiming to be bat guano must be consistent with the following definition:

Bat guano is partially decomposed bat excrement, with an “as is” organic matter content greater than 40%. Bat Guano is a source of nitrogen (N), and may contain up to 6% available phosphate (P2O5).