/pəˈpɪlə/
Noun, plural papillae
1. A nipple-like anatomical structure. (wiktionary.org)
2. A small projecting body part similar to a nipple in form: as (merriam-webster.com)
a : a vascular process of connective tissue extending into and nourishing the root of a hair, feather, or developing tooth
b : any of the vascular protuberances of the dermal layer of the skin extending into the epidermal layer and often containing tactile corpuscles
c : renal papilla
d : any of the small protuberances on the upper surface of the tongue
3. (Botany) a tiny outgrowth on the surface of a petal or leaf. (wordnetweb.princeton.edu)
4. A small nipple-shaped protuberance concerned with taste, touch, or smell. (wordnetweb.princeton.edu)
5. A small projection of tissue at the base of a hair or tooth or feather. (wordnetweb.princeton.edu)
Word origin: From Latin papilla “nipple,” diminutive of papula “swelling”