Writing about back-formation earlier this year, I said that enthuse – a verb back-formed from enthusiasm – occupied a grey area of acceptability. This area is worth mapping in more detail, since much of what people say about enthuse applies to other words and usages, and offers insights into what Macmillan Dictionary calls real grammar.
Some people do not enthuse about enthuse, to say the least. Bryan Garner, in A Dictionary of Modern American Usage, says it is ‘avoided by writers and speakers who care about their language’. This is wishful thinking: Garner doesn’t like enthuse and doesn’t want others using it. So he implies that anyone who does use it doesn’t care about English, which is untrue and unfair.
For instance: In her post on the popular construction ‘How [adjective] is that?’, Gill Francis referred to ‘adjectives used to enthuse about a situation’. I know for a fact that Gill cares about English, and about language generally. People use enthuse because it suits the needs of expression at a given moment: clarity, precision, tone, efficiency, and so on. It does not mean they don’t care about English.
Lots of words and usages are criticised or considered ‘incorrect’ when really they’re just colloquial, relatively new, or unsuited to formal use. As Michael Rundell wrote recently, ‘what might be inappropriate in a very formal setting may be perfectly acceptable in a conversation between friends’. Macmillan Dictionary Blog is a friendly place, where we communicate in normal rather than formal style. So enthuse is fine here.
Garner also says enthuse is ‘widely criticized’, and here he is correct. The word is often censured by prescriptivist usage commentators, though it has been around for almost two centuries. Richard Grant White, in Words and Their Uses, called enthused a ‘ridiculous word’ and proposed enthusiasmed as a better-formed alternative – perhaps not entirely seriously. The National Geographic style manual, echoing Garner, says enthuse(d) is ‘avoided by careful writers’. Even the OED calls it ‘ignorant’, in an entry that will surely be revised.
What one generation finds ignorant or ridiculous, the next might adopt without fuss. Enthuse retains a semblance of impropriety, and is still frowned on by conservative writers and readers. Others, myself included, may have nothing against it but prefer periphrastic alternatives like ‘show enthusiasm’ or ‘be enthusiastic’.
For all the disapproval of enthuse, it is becoming more widespread and acceptable, showing up even in such publications as the New Yorker. The Columbia Guide to Standard American Usage considers it standard ‘in all but the most Formal and Oratorical uses’. Enthused in particular has soared in both American and British usage. If you’re writing something very formal or literary, you should probably avoid it. Otherwise, you can choose to use enthuse.

Stan:
I refuse to use enthuse,
But others can, if they choose.
Marc:
It’s one of many back-formations
I use, but only in quotations.
One may dislike a word because of a dislike for the thing it refers to;
or like a word for the precision with which it nails down a pet peeve or universal vice.
That’s true, Roger. Some of the criticism enthuse has received may owe partly to a dislike of effusiveness.