If you own housing that you rent out more than you use it yourself, you're a landlord.
If you rent out your house or apartment while you're on vacation, I wouldn't call you a landlord. But if you have a house or apartment that you only ever offer on AirBNB without ever using it yourself, you're a landlord.
Btw, I don't agree that being a landlord makes you deserving of a guillotine, but I do agree that we should limit the ownership of housing to natural persons, with a limit on how much space a person can own.