What's in a name?

I am indebted to my colleague for explaining that 'Air' is the name of a young person's popular beat combo but am left pondering the use of the adjective mobile in connection with phones.

JD would doubtless point out that the mobility in this case refers to the fact that the phone does not have to be attached to a landline. However, a landline phone is clearly mobile in that it can be picked up and moved, and surely it remains a phone even when it is disconnected. Similarly, doesn't a mobile phone remain a phone when it has been moved into an area where it cannot transmit or receive messages?

A trivial point, no doubt, but it opens up a wider discussion over defining things and people by their roles. Is a phone a phone when it is disconnected? Is a gunman by profession still a gunman when he has no gun? Are JD and I sub editors when we are not subbing copy? And would I have time to ponder such issues if the writers in our care took less time to return proofs?