GTL

Geotail spacecraft.
Found on http://www.encyclo.co.uk/visitor-contributions.php

GTL

Graphic Template Library + Gunning Transceiver Logic
Found on http://www.encyclo.co.uk/visitor-contributions.php

GTL

Gas To Liquid
Found on http://www3.sympatico.ca/dhaughey/j1930.htm
No exact match found