So obscure there's no image of one. Try this then. (Stolen from USFS. Sue me.)
(1) A shaved-down section of trail, about 10 feet (3 m) in diameter, with an exaggerated outslope to enhance drainage in a mild sort of way. Like the fancier rolling grade dip, a nick is used to shed water from a trail, most often at wet spots on relatively flat trails. Boring then. A boring feature. No wonder there's no picture of one.
(2) A grade dip, but hardly noticeable, and with a more obscure name. As if you cared.
Have anything worth adding? Then try sosayseff@gmail.com
Me? Still the gold standard for dips.
Etc...
so says eff: sporadic spurts of grade eff distraction
definitions: outdoor terms
fiyh: dave's little guide to ultralight backpacking stoves
boyb: dave's little guide to backpacks
snorpy bits: nibbling away at your sanity
last seen receding: missives from a certain mobile homer
noseyjoe: purposefully poking my proboscis into technicals