sulcus (n.) Look up sulcus at Dictionary.com
plural sulci, "fissure between convolutions of the brain," 1833, from medical use of Latin sulcus "furrow, trench, ditch, wrinkle," apparently literally "the result of plowing," from PIE *selk- "to pull, draw" (cognates: Greek holkos "furrow," Old English sulh "plow," Lithuanian velku "I draw").