The dictionary's not wrong, it's just not perfectly accurate. You can look up introversion, but a one sentence summary is never going to be as good as, say, reading everything Freud and Jung wrote.
I find I'm introverted and shy. I prefer to live in my own head, but the occasions when I have to venture outside can be painful and awkward. I found my shyness diminished as I got older. It went from spending six hours walking around outside a library too nervous to speak to the person on the counter, to giving talks and seminars. However, I still find myself unexpectedly paralysed at odd times, like when I have to call a stranger on the phone.