I have used "irascible smile" when talking of a friend who is almost always smiling. I was asked to define the word by someone unfamiliar to its use, and reached for the dictionary (electronically) to explain it, where I found the latin-derived definition of 'quick to anger' in various paraphrasings.
I know the words from reading it as I have mentioned, and from phrases such as 'irascible old man', 'irascible youth' so I understood it to be more along the lines of 'easily provoked' where the context makes it clear in what way (joy, anger, etc).
Am I alone in this misunderstanding? Is this a valid use of the word? If not, can you suggest words that fit better for my intended meaning? (I have thought of irrepressible as a good alternative).