Patric Lewandowski offers this video lecture of his attempt to define comics, based on his earlier column from Comixtalk. He covers a lot of ground, meshing numerous memes of comics theory.
Ultimately, I do disagree with most of his points, for reasons I've described elsewhere**, but it's at least interesting to see him present it all together, and I do like that other people are at least trying to address these issues.
While I've defended people's attempts to define comics before, from the visual language perspective, the whole issue of "defining comics" does seems a little strange, and likely stems from McCloud's big thrust to do so in Understanding Comics.
McCloud's guiding rhetoric was a division of form and content. For him, the form was comics and the content was the genres that appear in comics. But, you can take this one further, since comics are only a "form" if you presume them to be.
Really, comics are made of two mediums: text and sequential images. These can be the "form" and the notion of "comics" is the content. Truly, as Patric tries to get at, text and/or images appear in lots of places, but only sometimes are they called "comics." This says to me that "comics" are not a thing definable by those elements at all as a type of "form."
Rather, comics are written in text and images the same way that novels or magazines are written in text. From this perspective, debates over "what are comics?" are rendered similarly to "what are novels?" or "what are magazines?"
**Though I will add emphatically that my theory of visual language as he presents it there is fairly misleading. Visual language is NOT just about iconography!!