depressant

n. someone or something that depresses; substance which depresses bodily activity (i.e. alcohol); sedative, drug that reduces tension and anxiety

adj. sedative, reducing the vital activities (Medicine); causing depression; reducing economic activity

A depressant, referred to in slang as a "downer," is a chemical agent that diminishes the function or activity of a specific part of the body. (See also sedative.) The term is used in particular with regard to the central nervous system (CNS). Alcohol (consumed in alcoholic beverages) is the most obvious example of a depressant. Many depressants acting on the CNS do so by increasing the activity of a particular neurotransmitter known as gamma-aminobutyric acid (GABA), although other targets such as the NMDA receptor, mu-opioid receptor and CB1 cannabinoid receptor can also be important, depending on which drug is involved.
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Noun
1. a drug that reduces excitability and calms a person
(synonym) sedative, sedative drug, downer
(hypernym) medicine, medication, medicament, medicinal drug
(hyponym) benzodiazepine
(derivation) depress, deject, cast down, get down, dismay, dispirit, demoralize, demoralise
Adjective
1. capable of depressing physiological or psychological activity or response by a chemical agent
(antonym) stimulative
(similar) ataractic, ataraxic, sedative, tranquilizing, tranquilising

(n.)
An agent or remedy which lowers the vital powers.
  

Synonyms and related words:
Amytal, Amytal pill, Demerol, Dial, Dolophine, H, Luminal, Luminal pill, M, Mickey Finn, Nembutal, Nembutal pill, Seconal, Seconal pill, Sulfonal, Trional, Tuinal, Tuinal pill, alcohol, amobarbital sodium, analgesic, anodyne, barb, barbital, barbiturate, barbiturate pill, barbituric acid, belladonna, black, black stuff, bleak, blue, blue angel, blue devil, blue heaven, blue velvet, bromide, calmative, cheerless, chloral hydrate, codeine, codeine cough syrup, depressing, depressive, depressor, dismal, dispiriting, dolly, downer, dreary, goofball, hard stuff, heroin, hop, horse, hyoscyamine, hypnotic, junk, knockout drops, laudanum, liquor, lotus, meperidine, methadone, morphia, morphine, narcotic, opiate, opium, oppressive, pacifier, pain killer, paraldehyde, pentobarbital, phenobarbital, phenobarbital sodium, purple heart, quietener, rainbow, red, reserpine, scag, scopolamine, secobarbital sodium, sedative, shit, sleep-inducer, sleeper, sleeping draught, sleeping pill, smack, sodium bromide, sodium thiopental, somnifacient, soother, soothing syrup, soporific, tar, thalidomide, tranquilizer, turps, white stuff, yellow, yellow jacket