No. Plain and simple. But let's break down your question. There are several aspects to the whole idea of 'word in a language' that make the question a lot more difficult to formulate properly. In fact, I'd say that there's two quite distinct questions in here that would require quite different disciplinary approaches.
Question 1. Is there a word that (either through loan or historical descent) occurs in the lexicon of all languages in such a way that through some empathetic effort could be made understood by its speakers regardless of their exposure other other languages?
The answer here is, no. The best candidate may seem 'mama' because it's associated with an early language development but it's not at all universal. Even the underlying concept is not unambiguously universal because of the variety of child rearing practices around the world.
Question 2. Is there a word that has had such global impact (through media or trade) that it will be recognized and/or understood by all people in the world regardless of whether it is a part of the lexicon in their language.
Again, the answer is a simple no. The most plausible candidate here is 'OK' that will be recognized by a good chunk of the global population. But there are vast swathes of the globe that will not have been reached by 'OK'. You don't even have to go as far as 'uncontacted tribes'.
There is simply too much variation among languages and cultures for there to be even a single universal word. However, there are many words that will certainly have a good chance of being understood around much of the industrialized world but never by all.
There probably not even too many gestures that are universal. 'Smile' and 'pointing' are probably the best candidates but their meanings are significantly modified by context across cultures so even though they may have the same underlying referent, their use could still be misunderstood.
