Almost totally agree--the only caveat is that there are some really misleading ways to use language that should be avoided even if doing a definition.

For instance, "I define 'no' to mean 'the'. I saw no dog on my walk today. I can't tell you how sick I am of seeing no dog on my walks." Or "user happiness is defined to be the number of times they click on the paste icon instead of hitting ^V".

But if the definition is made in good faith, I agree--just work with it.