Example: I encounter the name Quintus Curtius Rufus in a book and want to look it up (else than just in wikipedia). If I select all three words, the option is not there. If I select any of the three, then I can use "lookup" from the context menu but of course the lookup is less specific and bound to come up with false positives. Other examples would include expressions such as sine qua non. "Show information" can sometimes do the trick but "lookup" would be better (in the case above, ie, Rufus, show information is useless, but using lookup in the command box does produce results).
