villus(n = noun.animal) - a minute hairlike projection on mucous membrane;
is a kind of appendage, outgrowth, process
has particulars: chorionic villus

1.  One of the minute papillary processes on certain vascular membranes; a villosity; as, villi cover the lining of the small intestines of many animals and serve to increase the absorbing surface. [1913 Webster]

2.  Fine hairs on plants, resembling the pile of velvet. [1913 Webster]

villus, n. (pl. villi)
1 Anat. each of the short finger-like processes on some membranes, esp. on the mucous membrane of the small intestine.
2 Bot. (in pl.) long soft hairs covering fruit, flowers, etc.

Derivative:
villiform adj. villose adj. villosity n. villous adj.

Etymology:
L, = shaggy hair

chorionic villus, chorionic villus biopsy, chorionic villus sampling