antibiotic

1 of 2

noun

an·​ti·​bi·​ot·​ic ˌan-tē-bī-ˈä-tik  -ˌtī-  -bē-ˈä- 

: a substance able to inhibit or kill microorganisms

specifically : an antibacterial substance (such as penicillin, cephalosporin, and ciprofloxacin) that is used to treat or prevent infections by killing or inhibiting the growth of bacteria in or on the body, that is administered orally, topically, or by injection, and that is isolated from cultures of certain microorganisms (such as fungi) or is of semi-synthetic or synthetic origin

Symptoms of campylobacteriosis include muscle aches, fever, cramps and diarrhea leading to gastrointestinal illness, which can be treated with antibiotics.

—Chicago Daily Herald

Another way to produce new variants of established antibiotics is to use genetic engineering to alter the biochemical pathways of the microbes that produce them.

—New Scientist

Experts agree that by spiking animal feed with antibiotics, conventional farmers are speeding the emergence of drug-resistant bacteria.

—Geoffrey Cowley

Note: While antibiotics are effective mainly against bacteria, they are sometimes used to treat protozoal infections. Some consider antibiotics to include only those derived fully or partly from microorganisms and exclude synthetic forms from this class of drugs.

antibiotic

2 of 2

adjective

1

: tending to prevent, inhibit, or destroy life

2

: of or relating to antibiotics or to antibiosis

antibiotic drugs

antibiotically

ˌan-tē-bī-ˈä-ti-k(ə-)lē, 

ˌan-ˌtī- 

-bē-ˈä-

adverb

Examples of antibiotic in a Sentence

Recent Examples on the Web

Noun

But Newman had a hunch that when soil dries up, the antibiotics bacteria use to wage war might become more potent, simply because of evaporation. —Jonathan Lambert, NPR, 27 Mar. 2026

Major dental work to remove her broken and decaying teeth, concentrated nutrition, antibiotics, vaccines, a spay surgery and an introduction to such simple luxuries as an indoor bed and gentle touch have all been part of Gertie’s healing. —News Release, San Diego Union-Tribune, 27 Mar. 2026

Adjective

The team then re-analyzed those soil samples from around the globe, looking for antibiotic resistance genes. —Jonathan Lambert, NPR, 27 Mar. 2026

The researchers also looked at soil data from several different ecosystems that had experienced drought and found elevated levels of antibiotic-resistant bacteria. —K. R. Callaway, Scientific American, 23 Mar. 2026

Word History

Etymology

Noun

derivative of antibiotic entry 2

Note: Noun use of the adjective antibiotic probably began in the early 1940's, preceded by the frequent collocation antibiotic substance, but was not common before Selman waksman's paper "What Is an Antibiotic or an Antibiotic Substance?" (Mycologia, vol. 39, no. 5 [September-October, 1947]). Waksman has been credited with coining antibiotic, though he does not claim to have done so, and in fact gives an account of the earlier history of the word in this article.

Adjective

borrowed from French antibiotique, derivative of antibiose antibiosis (after symbiose symbiosis : symbiotique symbiotic)

Note: See note at antibiosis.

First Known Use

Noun

1943, in the meaning defined above

Adjective

1891, in the meaning defined at sense 1

Rhymes for antibiotic

• antipsychotic
• antithrombotic
• epizootic
• homoerotic
• psychoneurotic
• unpatriotic
• xenobiotic
• abiotic
• aeronautic
• apoptotic
• asymptotic
• cyanotic

Kids Definition

antibiotic

noun

an·​ti·​bi·​ot·​ic

ˌant-i-bī-ˈät-ik, 

ˌan-ˌtī-, 

ˌant-i-bē-

: a substance produced by an organism (as a fungus or bacterium) that in dilute solution inhibits or kills a harmful microscopic plant or animal and especially one that causes disease

antibiotic adjective

Medical Definition

antibiotic

1 of 2 adjective

an·​ti·​bi·​ot·​ic -bī-ˈät-ik; -bē- 

1

: tending to prevent, inhibit, or destroy life

2

: of or relating to antibiotics or to antibiosis

antibiotically

-i-k(ə-)lē 

adverb

antibiotic

2 of 2 noun

: a substance able to inhibit or kill microorganisms

specifically an antibacterial substance (as penicillin, cephalosporin, and ciprofloxacin) that is used to treat or prevent infections by killing or inhibiting the growth of bacteria in or on the body, that is administered orally, topically, or by injection, and that is isolated from cultures of certain microorganisms (as fungi) or is of semi-synthetic or synthetic origin

Note: While antibiotics are effective mainly against bacteria, they are sometimes used to treat protozoal infections. Some consider antibiotics to include only those derived fully or partly from microorganisms and exclude synthetic forms from this class of drugs.