There doesn't seem to be a formal definition of what constitutes a microstate.
I propose using the Wikipedia definition:
'A microstate is a sovereign state having a very small population or very small land area, but usually both. The connection is restricted to sovereign states with an area less than 1000 km² AND fewer than a million people.'
There are 24 entities in the world that fit this description (see
microstates). Cyprus, Lebanon etc. are therefore not admitted. They belong more to the Belgium-Israel league.
If anybody knows of a better one, please let us know!