Never-ending describes something that seems to go on for a very long time, as if it will not stop. We say a never-ending queue, never-ending rain, a never-ending list of jobs. Though actually, it is often a feeling, not a cold fact: the queue will end, but it does not feel that way while you wait. People use it a lot in everyday talk, a little loosely, to complain or to joke. It is not a hard scientific word. You will usually see it with a hyphen (never-ending); that is the form dictionaries like.