Wiktionary
n. The short, wooly underfur of certain animals, especially sheep.
Usage examples of "underwool".
As chance provided, the white wool of mouflon which was shed naturally by the wild sheep in spring, the unbelievably soft earthy-brown downy wool of musk-ox, and the lighter red rhinoceros underwool were also gathered with great enthusiasm.
A sighting of the enormous, unpredictable rhinos, with two horns, the front one long and low-slung, and two coats of reddish fur, a soft downy underwool and an outer layer of long guard hair, always brought exclamations of wonder.
She also noticed headbands and belts, and across the shoulders of the girl, a cape with fascinating designs that were worked into a material which appeared to have been constructed out of strands of the underwool shed by the passing woolly beasts.
Though their underwool was shed in summer, musk-oxen became stressed if the weather turned too warm.
The underwool from the yearlings or the ewes was equally soft, but not as strong under duress.