Acute

1. Brief, quick, short.

Synonyms: fast, rapid

Antonyms: leisurely, slow

2. High or shrill.

Antonym: grave

3. Intense, sensitive, sharp.

Synonyms: keen, powerful, strong

Antonyms: dull, obtuse, slow, witless

4. Urgent.

Synonyms: emergent, pressing, sudden

5. (botany) With the sides meeting directly to form an acute angle (at an apex or base).

Synonym: obtuse

6. (geometry) Of an angle: less than 90 degrees.

Antonym: obtuse

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

Synonym: acute-angled

Antonyms: obtuse, obtuse-angled

8. (linguistics, chiefly historical) Of an accent or tone: generally higher than others.
9. (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.
10. (medicine) Of a short-lived condition, in contrast to a chronic condition; this sense also does not imply severity.

Antonym: chronic

11. (orthography) After a letter of the alphabet: having an acute accent.