Merriam-Webster Collegiate Dictionary - acute

 adjective  (~r; ~st)  Etymology: Middle English, from Latin acutus, past participle of acuere to sharpen, from acus needle; akin to Latin acer sharp — more at edge  Date: 14th century  1.  a.  (1) characterized by sharpness or severity ~ pain  (2) having a sudden onset, sharp rise, and short course ~ disease  (3) being, providing, or requiring short-term medical care (as for serious illness or traumatic injury) ~ hospitals an ~ patient  b. lasting a short time ~ experiments  2. ending in a sharp point: as  a. being or forming an angle measuring less than 90 degrees an ~ angle  b. composed of ~ angles an ~ triangle  3.  a. of an accent mark having the form ?  b. marked with an ~ accent  c. of the variety indicated by an ~ accent  4.  a. marked by keen discernment or intellectual perception especially of subtle distinctions ; penetrating an ~ thinker  b. responsive to slight impressions or stimuli ~ hearing  5. felt, perceived, or experienced intensely ~ distress  6. seriously demanding urgent attention an ~ emergency  • ~ly adverb  • ~ness noun Synonyms:  ~, critical, crucial mean of uncertain outcome. ~ stresses intensification of conditions leading to a culmination or breaking point an ~ housing shortage. critical adds to ~ implications of imminent change, of attendant suspense, and of decisiveness in the outcome the war has entered a critical phase. crucial suggests a dividing of the ways and often a test or trial involving the determination of a future course or direction a crucial vote.  Synonym: see in addition sharp.