As someone who writes a lot of Python, I'd say a Python blob is a half-formed idea expressed in Python without any particular thought given to design or conceptual clarity. Just enough to get the job done if you don't encounter any surprises, but not something you'd want to maintain. You expect it not to handle all of the edge cases and when it raises an exception you jump in and code around it at the point where it's raised, rather than fixing the root cause, which is lack of design. Unfortunately, a lot of Python starts out like this and then ends up being maintained anyway.

edit: What makes it blobbly is its lack of structure. It doesn't express any clear idea of the domain and tends to devolve into spaghetti.