strep·to·coc·cus (str?p?t?-k?k??s)n. pl. strep·to·coc·ci (-k?k?s?, -k?k??) Any of various round gram-positive bacteria of the genus Streptococcus that occur in pairs or chains and can cause various infections in humans, including strep throat, erysipelas, and scarlet fever.strep·to·coc·cal (-k?k??l), strep·to·coc·cic (-k?k?s?k, -k?k??k) adj.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.streptococcus (?str?pt???k?k?s) n, pl -cocci (-?k?ka?; US -?k?ksa?) (Microbiology) any Gram-positive spherical bacterium of the genus Streptococcus, typically occurring in chains and including many pathogenic species, such as S. pyogenes, which causes scarlet fever, sore throat, etc: family Lactobacillaceae. Often shortened to: strep streptococcal, streptococcic adjCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014strep?to?coc?cus (?str?p t??k?k ?s) n., pl. -coc?ci (-?k?k sa?, -si) any of several spherical bacteria of the genus Streptococcus, occurring in pairs or chains, species of which cause such diseases as tonsillitis, pneumonia, and scarlet fever. [1875?80;