Is the phrase "transmembrane segment" equivalent to the transmembrane domain of a protein?
Yes
I'll admit defeat in trying to find the section in the text you linked - if there's any one thing Google can't do, it's search.  But questions like this are better put to Uniprot, which gives quite a bit of information.  Following that link, you'll see they identify 21 AA of transmembrane topology from 698 to 718, with a cytoplasmic domain afterward.  So the cytoplasmic tail is the intracellular domain.
In a sense there is a second transmembrane domain - the signal peptide from 1-19 - but because it is cleaved little attention is paid to it.  The extracellular domain starts at 20, with an N terminus outside the cell.
To quote Wikipedia, a transmembrane domain &quot;usually denotes a single alpha helix of a protein&quot;.  You should probably listen to them on such an issue because nobody is more fixated on semantics (it's a sort of vote).  Philosophically, you can picture that multiple transmembrane segments could operate as a functional unit - but each of these segments would be separated by some region of extracellular or intracellular sequence from the next.  A &quot;domain&quot; in a protein is a self-contained unit in the primary sequence, not just a series of helices that turn out to be near each other, so that wouldn't work.  And in fact if you look at a GPCR paper they speak in standard terms of seven transmembrane domains even while analyzing how they function together.