Spot the Frippet: something sulcate.

 Something sulcate is marked with long parallel grooves.

That might be a ploughed field:

SA Mathieson / Ploughed field near Kingstanding Farm / CC BY-SA 2.0

or a column:

Pompeii, Italy Photo by Jebulon

or a sea shell:

photo by H. Zell

or a tortoise shell:

African spurred tortoise, Las Vegas Zoo

Stems are sometimes sulcate, too (look at an old tomato plant stem, for instance).

Or,  you never know, perhaps you yourself are pretty groovy...

...well, it's a nicer way of putting it than wrinkly, isn't it.

Spot the Frippet: something sulcate. The Latin word sulcus means a furrow.