When will you learn that there isn't a word for everything?
Some experiences slip through language, and insisting on a perfect label for them is a kind of impatience. The question has a tender, slightly exasperated tone, like someone speaking to a person who keeps demanding that grief, love or longing be named precisely before they will accept it. The quote suggests that meaning can exist without a word to hold it, and that silence or a clumsy gesture can sometimes say more than a definition.
The thought belongs to an old and wide tradition. Mystics have long said that the deepest things resist description, and Wittgenstein's remark that we must be silent about what we cannot speak of is a famous modern version. Krauss's fiction, which dwells on loss, memory and the strain of finding language for them, fits that outlook, though I would not lean too hard on any single source for the line.
In daily life, imagine a friend has just lost a parent and you are tormented by not knowing the right thing to say. This idea lets you stop hunting for the perfect sentence. You can say, "I don't have words, but I'm here," and then sit with them, make tea, and listen. The missing word is not a failure, just part of the moment.