Adjective

(en adjective)

Producing harm in a stealthy, often gradual, manner.

* 1847 , George Lippard, The Quaker City: or, The monks of Monk-Hall

Strong and vigorous man as he looks, Livingstone has been for years the victim of a secret and insidious disease.

* 1997 , Matthew Wood, The book of herbal wisdom: using plants as medicine

At some point in time they may become the source of an insidious cancer.

* 2007 , Sharon Weinstein, Ada Lawrence Plumer, Principles and practice of intravenous therapy

The nurse always must be alert to signs of slow leak or insidious infiltration.

Intending to entrap; alluring but harmful.

* Nathaniel Hawthorne

The insidious whisper of the bad angel.

* 1948 , D.V. Chitaley (editor or publisher), All India Reporter , volume 3, page 341:

All these facts clearly appear to me now to establish that the sanctioned scheme was a part of a bigger and […] more insidious scheme which was to hoodwink the creditors and to firmly establish and consolidate the position […]

* 1969 , Dorothy Brewster, John Angus Burrell, Dead reckonings in fiction

The atmosphere of this insidious city comes out to meet him the moment he touches the European shore; for in London he meets Maria Gostrey just over from France.

* 2005 , Anita Desai, Voices in the City , page 189:

This seemed to her the worst defilement into which this insidious city had cheated her and in her agitation, she nearly ran into the latrine, […]

* 2007 , Joseph Epstein, Narcissus Leaves the Pool , page 171:

This is the insidious way sports entrap you: you follow a player, which commits you to his team. You begin to acquire scraps of utterly useless information about teammates, managers, owners, trainers, agents, lawyers.

Hansel and Gretel were lured by the witch’s insidious gingerbread house.

(nonstandard) Treacherous.

* 1858 , Phineas Camp Headley, The life of the Empress Josephine: first wife of Napoleon

But with whom do you contract that alliance? With the natural enemy of France — that insidious house of Austria — which detests our country from feeling, system, and necessity.

* 1912 , Ralph Straus, The prison without a wall

‘Believe me,’ he shouted, ‘these insidious folk talk dangerous nonsense. I hear they are spouting out their ridiculous platitudes not five miles from this park in which we are standing…’

The battle was lost due to the actions of insidious defectors.

Adjective

(en-adj)

Urgent.

Sensitive.

Short, quick, brief.

* {{quote-magazine, year=2013, month=July-August, author= Philip J. Bushnell

, title= Solvents, Ethanol, Car Crashes & Tolerance, magazine=(American Scientist) , passage=Surprisingly, this analysis revealed that acute exposure to solvent vapors at concentrations below those associated with long-term effects appears to increase the risk of a fatal automobile accident. Furthermore, this increase in risk is comparable to the risk of death from leukemia after long-term exposure to benzene, another solvent, which has the well-known property of causing this type of cancer.}}

(geometry) Of an angle, less than 90 degrees.

(geometry) Of a triangle, having all three interior angles measuring less than 90 degrees.

(botany, of leaves) With the sides meeting directly to form a pointed acute angle at the apex, base, or both.

(medicine) Of an abnormal condition of recent or sudden onset, in contrast to delayed onset; this sense does not imply severity (unlike the common usage).

(medicine) Of a short-lived condition, in contrast to a chronic condition; this sense also does not imply severity.

* {{quote-magazine, year=2013, month=May-June, author= Katie L. Burke

, title= In the News , volume=101, issue=3, page=193, magazine=(American Scientist) , passage=Bats host many high-profile viruses that can infect humans, including severe acute respiratory syndrome and Ebola. A recent study explored the ecological variables that may contribute to bats’ propensity to harbor such zoonotic diseases by comparing them with another order of common reservoir hosts: rodents.}}

(orthography, after a letter) Having an acute accent.

High or shrill.

an acute tone or accent