rash

¹ American  

[rash] / ræʃ /

adjective

rasher, rashest

1. acting or tending to act too hastily or without due consideration.

   Synonyms:

   foolhardy, indiscreet, precipitate, incautious, venturous, reckless, impetuous, hasty

   Antonyms:

   cautious

2. characterized by or showing too great haste or lack of consideration.

   rash promises.

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rash ² American  

[rash] / ræʃ /

noun

1. an eruption or efflorescence on the skin.

2. a multitude of instances of something occurring more or less during the same period of time.

   a rash of robberies last month.

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rash ¹ British  

/ ræʃ /

adjective

1. acting without due consideration or thought; impetuous

2. characterized by or resulting from excessive haste or impetuosity

   a rash word

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rash ² British  

/ ræʃ /

noun

1. pathol any skin eruption

2. a series of unpleasant and unexpected occurrences

   a rash of forest fires

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Usage

What does rash mean? Rash describes acting too quickly and without proper planning, as in James was rash when he decided to quit his job after just one hard day. Rash also describes a great haste or a lack of consideration, such as Sahad avoided making rash decisions by doing a lot of research first. A rash is a skin condition, such as bumps or a red area, like you might get if you touch poison ivy. A rash is also several instances of something that occur at the same or nearly the same time, such as a rash of snowstorms over a week or a rash of electronic sales during the winter holidays. Example: He always jumps head first into rash decisions, but sometimes it works out.

Other Word Forms

Derived Forms

• rashlike
  adjective
• rashness
  noun
• rashly
  adverb

Etymology

Origin of rash¹

First recorded in 1350–1400; Middle English; cognate with Dutch, German rasch “quick, brisk,” Old Norse rǫskr “brave”

Origin of rash²

1700–10; < French rache (obsolete), Old French rasche skin eruption, derivative of raschier to scratch, ultimately < Latin rādere to scratch

Explanation

A rash is something that spreads like wild fire — red itchy skin or a series of unfortunate events. It can also describe an impulsive, wild decision. As an adjective, rash has meant "quick, vigorous" since the 1300s by way of Scotland. The meaning shifted to "reckless" a few hundred years later, and can still be used that way — a "rash decision" is a sudden, not well thought out one. Rash, the noun that no one wants on their skin, came a few hundred years after that, but from the French word rache which at some point meant "ringworm." Ringworm still gives us a red, itchy rash. Fun! Rash can also mean a lot of unpleasant things happening in a short amount of time, like robberies or earthquakes.

Example Sentences

She had a medical assessment booked for April 2025, but in March developed a rash which did not clear with pharmacy creams.

From BBC • Jun. 9, 2026

Diogo Mónica, who has amassed sizable positions in a number of startups over his career, set up a plan to avoid rash decisions.

From The Wall Street Journal • Jun. 9, 2026

The most common side effect is a prominent skin rash, which affected more than 86% of patients in the study.

From Science Daily • Jun. 4, 2026

This is a guy who is prone to rash decisionmaking and poor judgment, whose empathy for others, including those closest to him, may have a limit.

From Slate • Jun. 2, 2026

But the rash Arnold saw a chance to strike a crucial blow.

From "George Washington, Spymaster" by Thomas B. Allen

Related Words

• audacious
• bold
• daring
• foolhardy
• hasty
• ill-advised
• ill-considered
• immature
• impetuous
• imprudent
• indiscreet
• irrational
• reckless
• thoughtless