The basic idea behind the Navajo word t’áadoo is that it serves to negate, much like doo…da. However, t’áadoo seems to impart a more subjective definite type of negative thought than the doo..da construction.
For most verbs, the word comes before the subject, object, and verb (in simple sentences at the very beginning), and the affected verb is nominalized with a -í. So “Don’t do that” (annoyed response) could be said “T’áadoo baa nanináhí!”. Keep in mind that not every instance of t’áadoo should be interpreted as a rankled reaction.
There are a few simple phrases with concrete meanings. T’áadoo le’é translates almost always into “things”. T’áadoo hazhó’ó is like saying “poorly (done)” or “not very well”.
You’ll notice that Navajo words with the t’áá- particle are hard to directly translate into English, due to its being used in many different ways.