Do blini have to be thin?
This seems to be more of a linguistic question to me.
It depends on who you ask. In the region where I live: not necessarily, both the American style and French crêpe style pancakes are sometimes called &quot;блин&quot; and &quot;блинчики&quot; (little pancakes).
But for a lot of people it's only the French thin ones. And they call the other one &quot;оладушки&quot;. (Read: oladushki)
It's not exactly defined by region as much as simply what you're used to.
Also: the word is also a curse word, although a very childish one. The English version might be 'crap', I  think.