penicillin
noun
pen·i·cil·lin ˌpe-nə-ˈsi-lən 
1
: any of several relatively nontoxic antibiotic acids of the general formula C9H11N2O4SR that are produced by molds (genus Penicillium and especially P. notatum or P. chrysogenum) or synthetically and are used especially against gram-positive cocci
also : a mixture of such acids
2
: a salt or ester of a penicillin or a mixture of such salts or esters
Example Sentences
Recent Examples on the Web The most famous lab mishap in science history, when mold contaminated one of Alexander Fleming's petri dishes, led to the 1928 discovery of the first antibiotic -- penicillin. 
Katie Hunt, CNN, 14 Sep. 2022 Or penicillin, the infection-fighting antibiotic derived from mold in 1928. Robert Pearl, Forbes, 13 June 2022 Some of the world's greatest discoveries were accidental, such as penicillin, plastic and gunpowder. Nuala Walsh, Forbes, 4 May 2022 In a move that could create troublesome waves later in time, Claire decides to beat Alexander Fleming by a few centuries and invent penicillin. Sharareh Drury, Variety, 1 Mar. 2022 In contrast, antibiotics can treat a whole type of bacteria, such as all Strep pneumoniae, unless the bacteria have developed resistance to penicillin, for example. Judy Stone, Forbes, 22 Jan. 2022 By the early 1940s, penicillin became widely available and was found to be a reliable cure, but the treatment was withheld from the study participants. Talia Herman, ProPublica, 1 Nov. 2021 So hedgehogs with this particular skin fungus would naturally be exposed to penicillin. Karen Hopkin, Scientific American, 8 June 2022 The family matriarch had been advised not to get a COVID-19 vaccine because of an allergy to penicillin and other health issues. Hayley Smith, Los Angeles Times, 12 May 2021 See More
Katie Hunt, CNN, 14 Sep. 2022 Or penicillin, the infection-fighting antibiotic derived from mold in 1928. Robert Pearl, Forbes, 13 June 2022 Some of the world's greatest discoveries were accidental, such as penicillin, plastic and gunpowder. Nuala Walsh, Forbes, 4 May 2022 In a move that could create troublesome waves later in time, Claire decides to beat Alexander Fleming by a few centuries and invent penicillin. Sharareh Drury, Variety, 1 Mar. 2022 In contrast, antibiotics can treat a whole type of bacteria, such as all Strep pneumoniae, unless the bacteria have developed resistance to penicillin, for example. Judy Stone, Forbes, 22 Jan. 2022 By the early 1940s, penicillin became widely available and was found to be a reliable cure, but the treatment was withheld from the study participants. Talia Herman, ProPublica, 1 Nov. 2021 So hedgehogs with this particular skin fungus would naturally be exposed to penicillin. Karen Hopkin, Scientific American, 8 June 2022 The family matriarch had been advised not to get a COVID-19 vaccine because of an allergy to penicillin and other health issues. Hayley Smith, Los Angeles Times, 12 May 2021 See More Word History
Etymology
New Latin Penicillium
First Known Use
1929, in the meaning defined at sense 1
Kids Definition
penicillin
noun
pen·i·cil·lin ˌpe-nə-ˈsi-lən
: an antibiotic that is produced by a mold and is used against disease-causing bacteria
Medical Definition
penicillin
noun
pen·i·cil·lin ˌpen-ə-ˈsil-ən
1
: a mixture of relatively nontoxic antibiotic acids produced especially by molds of the genus Penicillium (as P. notatum or P. chrysogenum) and having a powerful bacteriostatic effect against various chiefly gram-positive bacteria (as staphylococci, gonococci, pneumococci, hemolytic streptococci, or some meningococci)
2
: any of numerous often hygroscopic and unstable amido acids (as penicillin G, penicillin O, and penicillin V) that have a structure in which a four-membered lactam ring shares a nitrogen and a carbon atom with a thiazolidine ring to which it is fused and that are components of the penicillin mixture or are produced biosynthetically by the use of different strains of molds or different media or are synthesized chemically
3
: a salt or ester of a penicillin acid or a mixture of such salts or esters