From BiblePortal Wikipedia

Baker's Evangelical Dictionary of Biblical Theology [1]

Uneasy feeling of uncertainty, agitation, dread, or fear. The most common words in Scripture translated as "anxious" or "anxiety" are the Hebrew deagaa [דְּאָגָה] (ten times in either the verbal or noun form) and the Greek merimna [Μέριμνα] (twelve times in either the verbal or noun form). Older English versions of the Bible often render these words as "thought, " "worry, " or "care."

In the Bible anxiety is frequently depicted as the common human reaction to stressful circumstances. Saul's father was anxious about his lost donkeys, and then about Saul's failure to return from looking for them ( 1 Samuel 9:5;  10:2 ). The psalmist confesses that anxiety is "great" within him ( Psalm 94:19 ). Anxiety is portrayed in the Scripture as being inconsistent with trust in God. David prays: "Search me, O God, and know my heart; test me and know my anxious thought" ( Psalm 139:23 ). Jesus' command, "do not worry, " which occurs six times in the Sermon on the Mount ( Matthew 6:25-33 ), is coupled with admonitions to trust in the heavenly Father. Paul urges: "Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God" ( Philippians 4:6 ). Anxiety frequently manifests itself in ungodly concern about provision, performance, or reputation, and appears to be rooted in incomplete knowledge, lack of control over circumstances, or failure to take an "eternal" perspective on things ( Matthew 6:25-34;  10:19;  Mark 13:11;  Luke 12:11-12,22-34 ). Occasionally, anxiety is a symptom of guilt ( Psalm 38:18 ).

Freedom from anxiety begins with confession that it is not God's will. In fact, anxiety is a subtle insinuation that God is either unable or disinclined to see to our welfare. Other remedial measures include recognizing the futility of worry ( Matthew 6:27;  Luke 12:25 ); cultivating a growing understanding of God's power and fatherly disposition ( Matthew 6:26;  Luke 12:30 ); entrusting to God the things that we cannot control ( 1 Peter 5:7 ); increasingly viewing things in eternal perspective ( Matthew 6:32-34;  Luke 12:30-34 ); and substituting prayer for worry ( Philippians 4:6 ).

Ralph E. Enlow, Jr.

See also Care

Bridgeway Bible Dictionary [2]

In a world where people face daily troubles and future uncertainties, it is natural that often they become anxious ( 1 Corinthians 7:32-33). Those who trust in God, however, need not be burdened by anxiety. God understands their troubles and concerns, and he promises them his peace if they cast their cares upon him ( Psalms 55:22;  Jeremiah 17:8;  Philippians 4:6-7;  1 Peter 5:7; see Peace ; Prayer ).

Jesus reassures Christians with the promise that since God gives them life, he can also give them whatever is necessary to maintain life ( Matthew 6:25-30). God is a loving Father who knows how to care for his children. To refuse to trust him is to act like those who do not know him ( Matthew 6:31-32; cf.  Luke 10:41-42;  James 4:13-16).

In fact, people’s anxiety concerning the affairs of life is often what prevents them from coming to know God. They refuse to give their serious attention to the one thing that can save them from anxiety, namely, the gospel of Jesus Christ ( Matthew 13:22). On the other hand, when people put God first by allowing him to reign in their lives, they find that he is able to relieve them of life’s natural anxieties ( Matthew 6:33-34).

Webster's Dictionary [3]

(1): (n.) A state of restlessness and agitation, often with general indisposition and a distressing sense of oppression at the epigastrium.

(2): (n.) Eager desire.

(3): (n.) Concern or solicitude respecting some thing or event, future or uncertain, which disturbs the mind, and keeps it in a state of painful uneasiness.

Holman Bible Dictionary [4]

 Philippians 2:20 2:28 2 Corinthians 11:28 Matthew 6:25-34 Mark 4:19 Luke 12:22-31 Matthew 6:33

Hastings' Dictionary of the New Testament [5]

See Care, Careful.