diseased
Americanadjective
adjective
Other Word Forms
Etymology
Origin of diseased
1425–75; late Middle English disesed; compare Anglo-French diseasé. See disease, -ed 2
Explanation
When something is unhealthy or affected by illness, it's diseased. Sadly, the diseased trees in the city park may eventually need to be cut down and removed. While this adjective essentially means "sick," it's not generally used to describe people. Instead, you might use it for plants, animals, or body parts: "Hepatitis can result in a diseased liver." Diseased comes from the Old French desaise, "discomfort or sickness," from des-, "without," and aise, "ease."
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Wacky animal sidekicks once felt vibrant in a holistic world of artifice; here, a goggle-eyed rooster just looks diseased.
From Los Angeles Times ● Jul. 9, 2026
One promising possibility would be to intercept Tau containing extracellular vesicles after they leave diseased neurons but before they reach healthy ones.
From Science Daily ● Jun. 30, 2026
In a study of mice, they found that a brain protein called Arc, which normally helps neurons communicate, also appears to help toxic Tau spread from diseased brain cells to healthy ones.
From Science Daily ● Jun. 30, 2026
Research focused on using chemotherapy and radiation to wipe out diseased bone marrow, then infusing healthy donor cells to create a new immune system capable of attacking cancer and rebuilding the body’s defenses.
From The Wall Street Journal ● Apr. 19, 2026
Her heart is the heart of a dying turtle: reptilian, dark-red, diseased.
From "Cat's Eye" by Margaret Atwood
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
