The Collaborative International Dictionary of English v.0.48:

Tat \Tat\ (t[a^]t), n. [Hind. [tsdo][=a][tsdo].]
   Gunny cloth made from the fiber of the Corchorus olitorius,
   or jute. [India]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tat \Tat\, n. [Hind. [.t]a[.t][.t][=u].] (Zool.)
   A pony. [India]
   [1913 Webster]

WordNet (r) 3.0 (2006):

tat
    n 1: tastelessness by virtue of being cheap and vulgar [syn:
         cheapness, tackiness, tat, sleaze]
    2: a projective technique using black-and-white pictures;
       subjects tell a story about each picture [syn: Thematic
       Apperception Test, TAT]
    v 1: make lacework by knotting or looping [syn: tat,
         intertwine]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

TAT
       Theoretical Arrival Time (GCRA)