My favourite sort of dipper is hard to spot even if it's there (which it nearly always isn't). It's a bird that looks like a bulky wren:
Italian dipper. Photo by Francesco Veronesi
which spends a lot of time underwater in shallow, fast flowing streams. When they blink you can see their startlingly white eyelids. I love them.
Still, if you fail to spot one of these beautiful birds then, rather neatly, you yourself are a dipper, because in bird watcher jargon to dip out means to miss a bird you've travelled especially to see, and to call such a person a dipper is a long-established joke.
There are other dippers, too. If you are a painter and have a small pot clipped to your palette for turps or water then that is a dipper. A car dips its headlights by means of a dipper. A dipper is slang for a pickpocket (now they are hard to spot).
On the other hand there are big dippers, which aren't hard to spot at all - although round here in Britain we call the starry one the plough:
and the fun fair one:
San Diego. Photo by Visitor7
a roller coaster.
Ah well. We can always fail to spot the bird, can't we?
Spot the Frippet: dipper. The word dip comes from the Old English dyppan and is related to the Old High German tupfen to wash.