Have you noticed how when you invite someone to something, and he or she responds, "Yes, I'd love to," you have to wait a millisecond to be sure that's the complete answer, and the person isn't going to say, "Yes, I'd love to, but..."? Polite discourse spends a lot of time in the conditional. Conversely, "No, I'd never do that," sometimes becomes "No, I'd never do that unless..." To be reluctant to do something is not always the same as not doing it.
Reluctance has, alas, all too tragically been in the news recently. The Myanmar government has been willing to accept international aid for its cyclone-stricken citizens, but reluctant to accept international aid workers to distribute it.
English has rather a rich vocabulary of reluctance, with a number of synonyms: to be averse, disinclined, hesitant to do something, or even to be loath to do it. This last one sounds particularly ferocious, related to concepts of fearsomeness, loathsomeness, ugliness, and, of course, the related transitive verb loathe, meaning to hate.
Reluctance, rooted in reluctari, to struggle against, suggests active resistance. That same root is present in the relentlessly fatalistic-sounding ineluctable, which means at bottom "that against which there is no point in struggling".
Hesitation and the words related to it are built on the ideas of irresolution, uncertainty, indecisiveness, and of a stammering tongue.
The English language developed its future tense out of expressions of volition. That's a highfalutin way of saying that "I will go" originally meant "I want to go". The implication was that if I want (desire) to go, I eventually will (future tense) go. But the link between intent and execution is not ironclad. And so all these expressions are better for describing someone's attitude than his or her precise action.
Not ruling out
If you hear, "He is reluctant" to do whatever, you assume he hasn't done it yet but don't rule out that he might do it some time.
And then, as if we don't have enough options here, the word reticent, from Latin meaning "tending to keep silent", is being pressed into service nowadays as well to mean "reluctant".
AskOxford.com includes this usage on a web page titled "For Better or Worse: Our Changing Usage". It lists "words and phrases that may ... be in the process of acquiring new meanings. Some are so well established in their new roles that they already appear in this guise in modern dictionaries, though often with a brief note explaining their parvenu status".
Only through the subtle zing of parvenu (French for "Johnny-come-lately") does Oxford signal any disdain for this particular set of developments. It cites an example: "An Irish seismologist, credited with having foretold the March 29 Indian Ocean earthquake, was reported to have commented: 'We are very reticent to use the word 'predict'.' Examples of the confusion are in plentiful supply on the internet.
For example, the Connecticut Post recently ran a story on a piece of legislation under the headline, "Healthcare bill goes before reticent Rell," a reference to Governor Jodi Rell. She wasn't quoted much in the piece but it was clear from context that what was meant was that she was reluctant to sign the bill. Reticent made for better alliteration, however.
It may be that in the age of Facebook and MySpace and tell-all TV talk shows and memoirs, nobody is reticent about anything anymore, and so we really don't need a word for the concept.