Action. Exercise, motion, movement, deed, performance; agency, force, operation; battle, conflict; gesture; representation, play; subject, plot; lawsuit, case.
Ant. Inertia, torpor, languor; quiescence, rest, passiveness; harmony, truce, peace.
Active. Agile, brisk, alert, lively, quick, prompt, ready, spry; industrious, energetic, busy, diligent.
Ant. Dull, idle, indolent, lazy, quiet, slow, stupid.
Actual. Real, true, genuine, certain, absolute, positive, veritable, substantial; present, sensible, perceptible.
Ant. Possible, fictitious, supposititious, virtual, theoretical, hypothetical, conjectural.
Acumen. Discernment, penetration, keenness, shrewdness, insight, sharpness, sagacity, acuteness.
Ant. Dulness, obtuseness, stupidity, bluntness.
Acute. Sharp, pointed, keen, shrewd; violent, intense; high, sudden, severe, distressing; subtile, ingenious, sagacious, discerning.
Ant. Dull, blunt, obtuse, stupid, heavy; chronic; stolid.