When John Ruskin first coined the term pathetic fallacy he truly did mean that people were committing a fallacy when describing inanimate objects as having characteristics (or having pathos so were, therefore, pathetic).
The more modern meaning, however, is pretty much the same literary technique, but as an actual technique rather than a fallacious over-description.
The phrase pathetic fallacy is a literary term for the attributing of human emotion and conduct to all aspects within nature. It is a kind of personification that is found in poetic writing when, for example, clouds seem sullen, when leaves dance, or when rocks seem indifferent. (Wikipedia)
The same article shows that the original meaning appears to have mostly survived in science, but it is considered fallacious in a more modern meaning of being logically false rather than Ruskin's original meaning of being simply a lie. Nowadays the fallacy is to attribute human characteristics to non-human concepts in scientific papers (although a good educational tactic for teaching science).
In science, the term “pathetic fallacy” is used in a pejorative way in order to discourage the kind of figurative speech in descriptions that might not be strictly accurate and clear, and that might communicate a false impression of a natural phenomenon. An example is the metaphorical phrase "Nature abhors a vacuum", which contains the suggestion that nature is capable of abhorring something. There are more accurate and scientific ways to describe nature and vacuums.