dilate

American  

[dahy-leyt, dih-, dahy-leyt] / daɪˈleɪt, dɪ-, ˈdaɪ leɪt /

verb (used with object)

dilated, dilating

1. to make wider or larger; cause to expand.

2. Archaic. to describe or develop at length.

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verb (used without object)

dilated, dilating

1. to spread out; expand.

2. to speak or write at length; expatiate (often followed by on orupon ).

dilate British  

/ ˌdaɪləˈteɪʃən, ˌdɪ-, daɪˈleɪt, dɪ-, daɪˈleɪtɪv, dɪ- /

verb

1. to expand or cause to expand; make or become wider or larger

   the pupil of the eye dilates in the dark

2. (intr; often foll by on or upon) to speak or write at length; expand or enlarge

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Related Words

See expand.

Other Word Forms

• dilatability noun
• dilatable adjective
• dilatational adjective
• dilation noun
• dilative adjective
• nondilatability noun
• nondilatable adjective
• overdilate verb
• redilate verb
• self-dilated adjective
• subdilated adjective
• undilatable adjective
• undilated adjective
• undilating adjective

Etymology

Origin of dilate

First recorded in 1350–1400; Middle English dilaten, from Middle French dilater, “to comment at length, enlarge,” from Latin dīlātāre “to spread out, widen,” equivalent to dī- di- ² + lāt(us) “wide” + -āre infinitive suffix

Explanation

To dilate something is to make it wider. When the light fades, the pupil of your eye will dilate, meaning it looks bigger. The verb dilate comes from the Latin word dilatare, which means “enlarge” or “spread out.” When something stretches, expands, or becomes wider, it is said to dilate. Usually the word dilate is used when the opening of something circular becomes larger, but every so often you might hear someone refer to the need to dilate someone's understanding of quantum physics, global warming, livestock breeding, or any other topic.

Example Sentences

Atropine eye drops are typically used to dilate the pupil before eye exams.

From The Wall Street Journal • Dec. 28, 2025

A typical remedy is to stretch or dilate the urethra, a minimally invasive procedure that is often performed with general anesthesia, Dr. Lepor said.

From New York Times • Feb. 12, 2024

At regular concentrations of about 1 percent, atropine is used to dilate the pupil for eye exams.

From National Geographic • Nov. 1, 2023

For example, the pupil tends to dilate during complex cognitive tasks or in response to unexpected stimuli.

From Science Daily • Oct. 24, 2023

The eyes seemed to expand and dilate until they filled the whole of Matthias’s vision.

From "Redwall" by Brian Jacques

Related Words

• expound