Gakuk
Words mean what people agree for them to mean. "Gakuk" is a word that I (Faré) use as a usual greeting in friendly IRC rooms. Since this word is used as such and known to be used as such, it can be considered to mean just that: a friendly greeting. But so as to fully grok the word "Gakuk", you must also consider that every person who is faced with my regularly using it will sooner or later ask me what "Gakuk" means, which is also a voluntary purpose of systematically using this word; hence, the word also functions as reminder of the conventional nature of the meaning of words, of the nature of rational communication as a cooperative way to build shared structures of information, etc. This, too, is part of "the" intended meaning of the word. And of course, none of these can ever be the meaning of the word, since meaning is conventional and relative, not sacred and absolute.I chose the word long ago, as the vocalization of some guttural sound that I imagined could be made by prehistoric ancestors, and have been using it on IRC since the early-to-mid-1990's. And yes, I've already been told since (though quite some time afterwards) that "kuk" means "dick" in swedish.
See also the word "grok", introduced in the book "Stranger in a Strange Land" by Robert A. Heinlein, who also uses it a lot without having to define it, its meaning emerging from its contexts of use.