What does rash mean?
Rash means impulsive, hasty, or lacking careful thought, especially when describing a decision or action. Calling a choice rash suggests that it was made before its risks or consequences had been properly considered; the term is generally formal and critical rather than neutral. Rash also names a sudden outbreak of spots or irritation on the skin, as in heat rash or a drug rash, and can rarely be used as a verb meaning to develop such an eruption. The word is useful because it captures both the speed of a decision and the implied lack of judgment. Its figurative use is much more common in editorial, political, and legal writing than in everyday conversation, while the medical sense is readily understood across both British and American English.
Acting or deciding without sufficient thought or caution; hasty and often reckless.
"The proposal would be rash without further testing."
Common in formal, editorial, and legal contexts; usually describes a decision, action, or reaction.
An outbreak of spots or irritation on the skin, especially one that appears suddenly.
"The doctor said the rash was an allergic reaction."
Common in medical and everyday descriptions of skin conditions.
To develop or break out in a rash.
"Her arms began to rash after trying the new detergent."
Relatively uncommon; more typical of formal or literary usage.
Used for multiple skin eruptions or separate instances of a rash.
"The child developed rashes after eating several different foods."
A rash decision can leave a lasting mark, just like a rash on the skin.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does rash come from?
The adjective comes through Middle English from an Old Norse word meaning vigorous or daring, in which sense it originally described bold or impetuous action. The noun meaning a skin eruption developed separately in Middle English from Old English ræsc, a word related to comparable terms in other Germanic languages. Modern usage retains the adjective's sense of acting with excessive haste and the noun's sense of a sudden skin eruption.
Related word forms
How rash is actually used
When used as an adjective, rash is formal and usually critical: it describes actions, decisions, or reactions that are made with too little thought. As a noun, it is common in medical contexts. The verb is relatively uncommon and is more typical of formal or literary usage.