I don't think there's a way to do this using the UI, but you should be able to do this using template_preprocess_field().
Store the full version of each acronym as the description on each of your taxonomy terms. The acronym would be the title.
Then you'll want to do something like:
*note that this is all pseudo-code as I don't have a version of Drupal handy to test this, but with some kpr() or var_dump() calls you should be able to debug it for your needs*
<?php
function my_theme_preprocess_field(&$vars) {
$element = $vars['element'];
// Modify the output of the taxonomy term field
if ($element['#field_name'] === 'field_my_taxonomy_term') {
// Get the title and description
$item = $vars['items'];
$acronym = $vars['items'][0]['title'];
$description = $vars['items'][0]['description'];
//create the html you want
$html = '<span>'.$acronym.' - '.$description.'</span>';
//now replace the default field markup with your new markup
$vars['items'][0]['#markup'] = $html;
}
}
?>