apprehensive

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Anxious or fearful about the future; uneasy.
• adjective Archaic Capable of understanding and quick to apprehend.

from The Century Dictionary.

• In the habit of seizing; ready to catch or seize; desirous to lay hold of: used literally and figuratively.
• Quick to learn or understand; quick of apprehension.
• Realizing; conscious; cognizant.
• In a state of apprehension or fear; feeling alarm; fearful.
• Inclined to believe or suspect; suspicious: as, I am apprehensive that he does not understand me.
• Perceptive; feeling; sensitive.
• In metaphysics, relating to simple apprehension.

from the GNU version of the Collaborative International Dictionary of English.

• adjective Capable of apprehending, or quick to do so; apt; discerning.
• adjective rare Knowing; conscious; cognizant.
• adjective Relating to the faculty of apprehension.
• adjective Anticipative of something unfavorable' fearful of what may be coming; in dread of possible harm; in expectation of evil.
• adjective rare Sensible; feeling; perceptive.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Anticipating something with anxiety or fear.
• adjective Perceptive; quick to learn; intelligent; capable of grasping with the mind or intellect.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• adjective mentally upset over possible misfortune or danger etc
• adjective quick to understand
• adjective in fear or dread of possible evil or harm