Semantic diffusion is what happens to a word that was coined by a person or group with a reasonably good definition and then spreads through the wider community in a way that weakens that definition — a weakening that risks losing the definition entirely, and with it any usefulness the term had. The term was coined by Martin Fowler in 2006, who described the mechanism as essentially a succession of the telephone game, in which people other than a term’s originators start talking about it without being careful to follow the original definition. It names a failure mode in technical vocabulary rather than a practice anyone carries out deliberately.
Usage
The term is used to diagnose why a piece of jargon has stopped being useful: not that it was badly defined at the outset, but that the definition did not survive the journey to its wider audience. Simon Willison, writing in March 2025, presents the reception of Vibe Coding as an instance of the effect — he had been complaining that the term was already being distorted to mean any time an LLM writes code, as against its intended meaning of code written with an LLM without the person reviewing what was written, and encountered Fowler’s term in the course of that complaint. His own account of the frustration is that “for a few glorious moments we had the chance at having ONE piece of AI-related terminology with a clear, widely accepted definition”, and that people could not be trusted to read Andrej Karpathy’s original post all the way to the end. He reports the same thing having happened to his own coinage, Prompt injection, over the preceding couple of years.
Willison regards this dilution of meaning as frustrating but apparently inevitable, and — attributing the point to Fowler — notes that it is most likely to happen to popular terms, on the reasoning that the more popular a term is, the higher the chance of a game of telephone in which misunderstandings multiply as the chain grows. What the effect does not appear to be is something a term’s originator can simply overrule: Karpathy, who coined vibe coding, replied to Willison’s article that it will take time to settle on definitions, and described his own practice as rarely going full out vibe coding — more often still looking at the code, adding complexity slowly, and trying to learn how the pieces work.
Related Terms
- Vibe Coding — the term whose dilution is presented here as a current example
- Prompt injection — an earlier coinage the same source reports as having undergone the same effect