10. Obsolete
What they think it means: Old, out of date.
What it actually means: Not produced, used, or needed.
You might think that your old cellphone is obsolete, and you might be right, because that model probably isn't produced anymore. However, cellphones on the whole are still produced, used and needed, so cellphones in themselves are not obsolete. A good example of something that is obsolete is a steam engine – they’re so inefficient compared to today’s combustion and electric engines, that no-one produces, uses or needs them.