You can spell out a word, rather than pronouncing it using Text Speaker.
For example, a computer program may have a "Graphical User Interface", which is abbreviated as "GUI". If you want Text Speaker to say "G U I" instead of "gooey" when it reads this abbreviation, you can mark it to be spelled.

Select the word or phrase to be spelled. Click on the 'Edit' menu and select 'Spell Selected Word/Phrase' option. The text will be enclosed within the tags <spell> and </spell>.

Now when you hear the particular word/phrase, it will be spelled out.