Correct spelling for the English word "theftuous" is [θˈɛft͡ʃuːəs], [θˈɛftʃuːəs], [θ_ˈɛ_f_tʃ_uː_ə_s] (IPA phonetic alphabet).
In Scots law, of the nature of theft; tainted with theft.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.