phlegm

American  

[flem] / flɛm /

noun

1. the thick mucus secreted in the respiratory passages and discharged through the mouth, especially that occurring in the lungs and throat passages, as during a cold.

2. one of the four elemental bodily humors of medieval physiology, regarded as causing sluggishness or apathy.

3. sluggishness, indifference, or apathy.

   Synonyms:

   impassiveness

   Antonyms:

   concern, animation

4. self-possession, calmness, or composure.

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phlegm British  

/ flɛm /

noun

1. the viscid mucus secreted by the walls of the respiratory tract

2. archaic one of the four bodily humours

3. apathy; stolidity; indifference

4. self-possession; imperturbability; coolness

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phlegm Scientific  

/ flĕm /

1. Thick mucus produced by the mucous membranes of the respiratory tract, as during a cold or other respiratory infection.

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Other Word Forms

• phlegmless adjective
• phlegmy adjective

Etymology

Origin of phlegm

1350–1400; Middle English fleem < Middle French flemme < Late Latin phlegma < Greek phlégma flame, phlegmatic humor, equivalent to phlég ( ein ) to burn + -ma resultative noun suffix

Explanation

Phlegm is a thick secretion of mucous. It's hard to sleep when you have a bad cold and your throat is full of phlegm. Your body's respiratory system creates phlegm, pronounced "flem," which becomes thicker and more annoying when you're ill. The thick substance you cough up when you have a terrible cold is phlegm. We don't talk about phlegm all that often these days, but it was very important in medieval science — it was thought that too much phlegm led to apathy and laziness, and it was a sign that the body was out of balance.

Example Sentences

She hocks back phlegm on a couple of occasions and violently rubs her tired eyes between questions.

From Los Angeles Times • Apr. 15, 2026

"It affects everyone because these toxins and heavy metals enter the body directly," he told AFP, describing "burning eyes, phlegm, and nasal inflammation."

From Barron's • Apr. 3, 2026

Spitting up black phlegm and shouting out strings of word-association gibberish, Ms. Buckley quickly becomes the centerpiece of the movie, or rather its central headache.

From The Wall Street Journal • Mar. 5, 2026

The four-humors theory—that illness came from imbalances in blood, phlegm, yellow bile, and black bile—was “common sense” to them.

From Slate • Sep. 26, 2025

He spat into the road a bloody phlegm.

From "The Road" by Cormac McCarthy