Vocabulary, terminology and definitions have to be adhered to, if one is to communicate clearly, without the danger of being misunderstood.

If you want to make up words, as did literary giants Lewis Carroll and Rudyard Kipling did, you'll still have to explain what you mean, unless you are happy to be misconstrued. Jabberwocky is a nonsense poem, where words have been completely made up, or were archaic words that still had a different meaning

However, we do redefine some words when using metaphors, as in the term literary giant, where we know not to take the word 'giant' literally. But we always risk being misunderstood when we use words loosely.

In terms of what a free thinker is, it isn't about redefining words, but being able to think imaginatively, without any constraint about anything, ignoring dogma, taboos, conventions or mores.

In many ways, science-fiction writers are free-thinkers, coming up with fantasy that often becomes science fact. Jules Verne wrote 'Rocket to the Moon' in 1865, over 100 years before it happened. If one wishes to achieve the impossible, one first has to define what impossible is.

As an example

“It is spring, moonless night in the small town, starless and bible-black, the cobbledstreets silent and the hunched courters'-and-rabbits' wood limping invisible down to the sloeblack, slow, black, crowblack, fishingboat-bobbing sea.”

Dylan Thomas, Under Milk Wood

Contours up images far better than descriptive prose.

A poet uses words in creative ways, and poets are IMO free thinkers, at least sometimes. The terms poet and free thinker aren't precisely defined so that readers precisely understand my implication. That is true of many words, including spirituality and common sense. My first thought was, "Common sense is the opposite of spirituality." Then I considered your intent and developed an idea of your meaning.

Yes, a free thinker may use poetic license to extend the meaning of words, but IMO it isn't as simple as saying Spirituality is a synonym for Common Sense. I'm not particularly good with nuances of language; though, I'm aware of them. I sometimes attempt to compose a poem, but my best efforts are merely rhymes, so far. It's a self improvement project, and a pass time to stave off boredom. On the other hand, free thinking seems natural and impossible to avoid. But, what is a free thinker?

If words ever did carry the essence of the object that was being signified, that day is gone. Some personal names, I think, still carry a meaning about the person. That old Scholastic relation of words to ultimate reality died a death with the introduction of nominalism. Generally speaking, words seems to be just pointers to thoughts and objects. We could talk about concepts such as good and bad as nominal concepts because we attributed the same meanings to words. That too has now died a death. Words mean what you want them to mean. Language and relativity have given birth to a chameleon that keeps changing its appearance. When Jesus allegedly tells Pilate that he came into the world to bear witness to truth, Pilate is supposed to have replied “What is truth?” The implication was, as Tim Rice wrote in Jesus Christ Superstar, that we all have truths and they differ from each other. At least they had words. Now we all have words but they have different meanings.