[1] : WordNet (r) 2.0

tack on
     v : fix to; attach; "append a charm to the necklace" syn: append,
          tag on, tack, hang on
see also:
append tag on tack hang on 

[2] : Moby Thesaurus II by Grady Ward, 1.0

31 moby thesaurus words for "tack on":
   add, adjoin, affix, agglutinate, annex, append, attach, burden,
   complicate, conjoin, decorate, encumber, glue on, hitch on, infix,
   join with, ornament, paste on, plus, postfix, prefix, put with,
   saddle with, slap on, subjoin, suffix, superadd, superpose, tag,
   tag on, unite with

Tack >> T Words
Tack, definition of term: Tack
tack_pag1.html