Description lists are already implemented by many processors. It would be nice to see them featured in standard markdown.
Python-Markdown, Kramdown, Maruku, php-markdown/extra and pandoc all use the following syntax
topic : description 1 : description 2
Kramdown allows multiple topics
topic 1 topic 2 : description > with nested markup
Pandoc raises an interesting point about lazy wrappings:
To see why laziness is incompatible with relaxing the requirement of a blank line between items, consider the following example:
bar : definition foo : definition
Is this a single list item with two definitions of “bar,” the first of which is lazily wrapped, or two list items? To remove the ambiguity we must either disallow lazy wrapping or require a blank line between list items.
The nice thing about this syntax for definition lists is that processors that do not understand it natively will produce a single paragraph with a colon in the middle:
<p>topic : description</p>