Adjective

(er)

Hard to grasp; not obvious or easily understood; barely noticeable.

The difference is subtle , but you can hear it if you listen carefully.

(of a thing) Cleverly contrived.

(of a person or animal) Cunning, skillful.

insidious

* 1623 , , act iv, scene 4,

Thy age confirmed, proud, subtle , bloody, treacherous.

Tenuous; rarefied; of low density or thin consistency.

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