(organic chemistry) Any of a range of iodinated derivatives of thyronine, especially 3,5,3',5'-tetraiodothyronine, thyroxine.

(microbiology) Initialism of toxin-antitoxin.

A crayfish or lobster.

A river in the Scottish Borders council area, Scotland, United Kingdom / A surname, from the river and the adjacent Blackadder House.