I hope you understand how many words from the dictionary you have been using wrong all this time. Off the top of my head, sphere. A word that describes absolutely no real-life object, as every single point on the surface of that object would have to be precisely the same distance from the center.
Want more? Clean. Spotless. Weightless (in most real life situations). Equal or same (again, in most real life situations). Or maybe some more special examples like second/minute. Defined either circularly as a reference to the other or very roughly as "depending on the periodicity of the radiation of a caesium-133 atom".
You go rewrite the technical dictionary while I think of a few more examples ;).