1. [n]  the surgical procedure of manually restoring a displaced body part
2. [n]  a locomotor response toward or away from an external stimulus by a motile (and usually simple) organism

TAXIS is a 5 letter word that starts with T.

1. \Tax"is\, n.
   In technical uses, as in architecture, biology, grammar,
   etc., arrangement; order; ordonnance.
   
   

2. \Tax"is\, n. [NL., fr. Gr. ta`xis a division or
   arrangement, fr. ta`ssein to arrange.] (Surg.)
   Manipulation applied to a hernial tumor, or to an intestinal
   obstruction, for the purpose of reducing it. --Dunglison.
   
   

["A Language Facility for Designing Database-Intensive Applications", J. Mylopoulos et al, ACM Trans Database Sys 5(2):185-207 (June 1980)].