Definition
A substance that slows the activity of the brain and spinal cord, reducing alertness, reaction time, judgment, and coordination. Alcohol is the most common example; many sedatives, tranquilizers, and certain prescription and over-the-counter medications also fall into this category.
Plain English
Something that slows down how your brain and nerves work, making you think and react more slowly.
Context Anchor
Seen in aviation medical and alcohol discussions, especially when explaining why alcohol affects pilot performance even when a person does not feel drunk.
Derivation
From Latin deprimere, meaning 'to press down.' A depressant 'presses down' the activity of the nervous system — slowing it rather than stimulating it. This helps explain why these substances reduce, rather than improve, performance.
Why Pilots Care
Alcohol acts as one, directly impairing judgment, reaction time, and decision-making critical to safe flight.
Intuition Check
Do not read “depressant” as only meaning “makes you depressed.” Here it means “slows the brain and nervous system,” even if the person feels relaxed, cheerful, or confident.
Example Sentence 1
Because alcohol is a central nervous system depressant, the FAA prohibits flying within 8 hours of drinking and at any blood alcohol level of 0.04 percent or higher.
Example Sentence 2
Any central nervous system depressant must be fully metabolized before a pilot can legally or safely operate an aircraft.