Pseudo refers to something not genuine, spurious, or a sham, according to the definition in the dictionary. Science, in simple terms, is the study of natural phenomena.
So, literally a pseudo-science is a study that does not represent natural phenomena. The study of economics is a prime example of pseudoscience, for nothing in economics refers to the principles of nature (as I explain in The State of Economics).
My definition of pseudo-science, however, is a little more stringent and implies the highest normalization of knowable truth related to natural phenomena. As I explain in the evolution of evolution, the highest normalization of truth (upstream) is what periodically obliterates the downstream evolution of its suboptimal past. Hence, in my identification of pseudoscience, I include the regurgitation of truths that have already expired.
Meaning, flat-earthers are pseudo-scientists, for they continue to explore the expired truths of natural phenomena. More convoluted versions of pseudoscience are promulgated by scientists who use consequential data to infer causation, consistently invalidated by nature’s entropy, and thus evolutionary false.
Einstein and Feynman were real scientists, as from the observance of natural phenomena, they concluded and proved the universe is guided by different rules than previously thought. A climate-change “scientist” is a collector of data from which an evolutionary incompatible inference to cause is suggested, without understanding the causal principles by which those suppositions can reliably be issued, proven, and replicated.
In summary, pseudoscience, in its best incarnation, is a study that confounds consequence with cause, leading, in the words of Nietzsche, to grave depravity of reason. In its worst incarnation a pseudoscience is not related to the workings of nature at all.