- (chemistry) tritium-deuterium, a type of hydrogen (H2) molecule
- The ISO 3166-1 two-letter (alpha-2) code for Chad.
- (American football, Canadian football) Abbreviation of touchdown.
- (neurology) Abbreviation of tardive dyskinesia.
- (politics) Abbreviation of Teachta Dála, a member of Dáil Éireann, the lower chamber of the Parliament of the Republic of Ireland.
- (military) Abbreviation of Territorial Decoration (previously awarded to officers who had more than 12 years commissioned service in the Territorial Army (UK)).
- (travel) Abbreviation of ticket designator.
- (video games) Abbreviation of tower defense.
- (Teachta Dála): In English the abbreviation TD is normally used, with TDs as the plural (the full form of which in Irish is Teachtaí Dála). The letters follow the name of the member when used as a title, e.g. Mr Bertie Ahern TD.
TD m pl (plural only)