A cloth or stuff made of matted fibers of wool, or wool and fur, fulled or wrought into a compact substance by rolling and pressure, with lees or size, without spinning or weaving.
source: Webster 1913
verb
mat together and make felt-like
Felt the wool.
source: WordNet 3.0
cover with felt
Felt a cap.
source: WordNet 3.0
change texture so as to become matted and felt-like
The fabric felted up after several washes.
source: WordNet 3.0
To make into felt, or a feltike substance; to cause to adhere and mat together.