>    <p>The <dfn>tiger</dfn>, <span xml:lang="la">Panthera tigris</span>, is a 
> large, striped Asian felid.</p>

I doubt that it was ever intended for this sort of overt definition.  It is
more for.

<p>The best known big cats of the modern world are the <dfn>tiger</dfn> and
<dfn>lion</dfn>.  The tiger is a large striped cat found in Asia....</p>

When seen in print, the highlighting of tiger and lion tell the reader that
they shouldn't worry that they have never heard about lions and tigers 
before, because the concepts are about to be introduced.