"Acute" can be used in the sentence "It is an acute emergency" to describe an urgent situation. If someone demonstrates the ability to think deeply and concisely, one might say "He has an acute mind."
"Acute" is an adjective derived from the Latin word "acutus," meaning "to sharpen." It refers to a critical situation or to a person with finely-honed reasoning skills and a "sharp" mind. The word can also be used in medicine to describe a sharp pain. In geometry, it describes an angle of less than 90 degrees, an "acute angle," or a triangle containing three such angles, an "acute triangle."