• If you’re using cloud to refer to EC2, use EC2 instead. It’s concrete and it means very real things about your deployment and scaling models as well as how you’re managing your infrastructure.
• If you’re using cloud to refer to some service which runs over the Internet, either refer to the service or just say the Internet. You don’t store your mail “in the cloud”, you host it with Google apps. You don’t backup “to the cloud”, you have your backups stored over the Internet with Mozy or Carbonite.
• If you’re using cloud to refer to the idea of some hosted application platform, just say the platform. You don’t run your python app “in the cloud”, you run it on AppEngine (or something else).
• If you’re using cloud to mean that you are using virtualization and have some management stack on top of it, then please just say you’re running in a virtualized environment.
• If you’re using cloud to refer to having your server infrastructure hosted in a virtualized environment by someone else, again, just say you’re running in a virtualized environment.
• If you’re using cloud to refer to a “visible mass of little drops of water or frozen crystals suspended in the atmosphere”, then congratulations, you can continue to use the word cloud. And thanks to Wikipedia for the definition

Following this simple idea will let you avoid the otherwise impossible to avoid discussion of the semantics of the word “cloud” and what you happen to mean about it and how you might be wrong and … This then means you’ll be that much closer to achieving whatever goal you hoped to achieve as you’ll spend less time talking and more time doing. And as an added benefit, you’ll avoid getting grumpy emails from me about the fact that you’ve used such a terribly over-used and under-meaninged term.