What does acumen mean?
The definition of acumen
A*cu”men, n.
Etym: [L. acumen, fr. acuere to sharpen. Cf. Acute.]

Quickness of perception or discernment; penetration of mind; the faculty of nice discrimination. Selden.

Synonyms
— Sharpness; sagacity; keenness; shrewdness; acuteness.