<i>doesn't grammaticalisation refer to only a change in the *meaning of a word, specifically when, it transforms in from something concrete and tangible to one with mere grammatical connotations? I am trying to think of an example, but am struggling with one.</i>

But that's kinda what I meant. The ablaut went from being a purely phonological phenomenon (that happened in other environments) to being one that was reanalyzed as being morphological. Some weak verbs in English have been reanalyzed as strong ones of the ablaut-series. This is slightly different from your definition, because it doesn't have to be words, but can be morphemes.

<i>I imagined that the word doesn't morph in either spelling or pronunciation, its meaning however undergoes a specific change.</i>

Not necessarily. One classic example of grammaticalization is howe the modern Greek future morpheme, <i>tha</i> developed out of <i>thelo ina</i> 'I wish that'.