A school correspondent writes to point to a change in usage. In my Discover Grammar (p. 37) I list some sentences where someone has used transitive and intransitive verbs wrongly. One of the examples is I'm using now. My correspondent's students point out that this is perfectly OK, these days, in the context of drug taking. And she asks: 'if the object is implied but ellipted, as in this case, is the verb actually still transitive?'
Transitivity is a shifting thing, indeed. That's why, in this book and elsewhere, I always talk about transitive and intransitive 'uses' of verbs. A verb has a potential to be either, and it never surprises me to see a previously transitive verb being used in an intransitive way, or vice versa. In fact, intransitive uses of use can be found from the Middle Ages, and the drug-using meaning is first recorded as long ago as 1953. The OED gives an example from William S Burroughs' novel, Junkie: 'it is practically impossible to stop using'.
I wouldn't call I'm using an ellipted transitive, because the meaning is different from a transitive use. It means 'taking drugs'. I'm using something has one of the various meanings of use, such as 'employ', 'make use of', and so on. This is typical of verbs which have both uses. Compare the contrast between the other examples on page 37 of Discover Grammar, such as The neighbours have moved their car and The neighbours have moved.
Another point to note is that ellipsis isn't a useful notion here because it's not clear what is actually being left out. Ellipsis, in the grammatical approach I follow, is explicitly identifiable from the context. For example, if I say I like apples and someone comments So do I, it's reasonable to talk about ellipsis because the 'full' form of the sentence is plainly So do I like apples. But when someone says I'm using, in isolation, just like that, it's impossible to say exactly what's been omitted.