How can I use Lion's "look up" feature without the trackpad?

Lion introduced the new "Double-tap with three fingers" to Look up, which pops up a small definition of whatever word you double-tap. Is there any way to invoke look up without the trackpad? For example, if I'm on a desktop Mac (with a normal mouse) is there any way to quickly look up a word by using this same look up feature?

Solution 1:

From this:

For years, Mac OS X has had a great shortcut for getting a quick definition of a word: Simply hover the cursor over the word, and press the keyboard shortcut Command-Control-D to bring up a little Dictionary popup. This still works in Lion, but it’s now much more fully featured and also has a great new way to access it.

Your looking for Cmd+Ctrl+D

_{PS: Thanks for asking, it actually made me look and learn something new}

Solution 2:

Have you tried right clicking…