That's pretty easy to understand and most people can comprehend that right off the bat. The idea of listening to news and music on the Internet is well established, and most people understand what the term downloading means. Depending on my cohort's tech level, he or she may immediately understand that this audio file can be transferred to an audio device or not. Sometimes, this conversation leads to the inevitable question: "Why is it called a podcast?"
To that I generally give the old 'iPod + broadcast' answer. In some cases (again depending on the tech level of my compatriot) the conversation may go into a discussion about the other opinions on where the word came from, but in general that's pretty much the meat of the conversation.
Maybe I'm a simpleton, but I have a hard time wrapping my head around some of the definitions I see on the Internet that attempt to explain what a podcast is.
Robert, from Awakended Voice
The New Oxford Dictionary is the closest definition to mine.
The problem with the first two definitions is that they focus on the mechanics rather than the pragmatic. Neither of them mention well understood concepts like radio or television. Consider the two definitions of a car:
A car is a vehicle made of a steel body on wheels. It moves forwards and backwards by means of an internal combustion engine powered by gasoline.
A car is like an automatic wagon which allows you to travel long distances in a short period of time and optionally carry passengers and other stuff.
Which definition immediately characterizes what a car is and what it's good for?
Dave Winer and Adam Curry envisioned a world where RSS feeds automagically downloaded shows into portable media players while happy netizens slept and dreamt of sugar plum fairies. 2 years later, the reality is that only about 50% of podcast listeners use a podcatcher or listen to shows on a portable device.
That's why definitions of podcasting that are formed primarily around the concept of the RSS feed or listening on a portable player aren't effective. The podience isn't doing either of those things all that much so defining the term within that framework is going to get you a glazed look most of the time.
Give them a description they can relate to by comparing podcasts to already well understood concepts.