1. Self-styled.
2. So-called.
3. Pretended, would-be.
Usually, all three of these are implied. Nearly always used despairingly.
From the French soi meaning 'oneself' and disant meaning 'saying'. Pronounced swa-dee-ZA (put some nasal into that last 'ZA' if you want to do it right). The last 'N' may be pronounced or not, as you like (swa-dee-ZAN).