| Acronym | Definition |
|---|
| TTSI➣Total Transcription Solutions, Inc. (est. 2001; Quezon City, Philippines) |
| TTSI➣Trail Termination Source Identifier |
| TTSI➣Toshiba Technical Services International (Japan) |
| TTSI➣Text to Speech Interface |
| TTSI➣Travelling to School Initiative (UK) |
| TTSI➣Thyrotroph T4 Sensitivity Index (pituitary-thyroid diagnostics) |
| TTSI➣Thorn Transit Systems International, Ltd. (UK) |
| TTSI➣Tandem Telecommunication Systems Inc. |
| TTSI➣Taxpayer Treatment Service Improvement |