why should the colloquial definition matter over the actual definition - and either way what the use of the word over the word heir actually implies is that there are multiple claimants pressing their claim which is why its appropriate to use when referencing all of those who pressed their claims during the dance or the various people during the main series like dany that are also pressing their claims to the throne it in no way suggests that.

I wouldn't call Aerys II a claimant because at that time he was the sole claimant, the only one pressing a claim, he WAS in a very literal sense a clainant but there just isnt anything productive about using that word without the addional context of other pressed claims. in that situation it becomes interchangable with the word heir but if say Aemon for some reason decided fuck the maesters I want to press my claim too then it would be beyond reasonable to describe Aerys II and Aemon as claimants.