An instrument of war; a light spear. "Fiery darts" (Ephesians 6:16) are so called in allusion to the habit of discharging darts from the bow while they are on fire or armed with some combustible material. Arrows are compared to lightning (Deuteronomy 32:23,42; Psalms 7:13; 120:4).
Source: Easton's Bible Dictionary
Dart
D'ART, n. Gr., a spear or lance.
1. A pointed missile weapon to be thrown by the hand; a short lance.
2. Any missile weapon; that which pierces and wounds.
And from about her shot darts of desire.
D'ART, v.t.
1. To throw a pointed instrument with a sudden thrust; as, to dart a javelin.
2. To throw suddenly or rapidly; to send; to emit; to shoot; applied to small objects, which pass with velocity; as, the sun darts his beams on the earth.
Or what ill eyes malignant glances dart. Pope.
D'ART, v.i.
1. To fly or shoot, as a dart; to fly rapidly.
2. To spring and run with velocity; to start suddenly and run; as, the deer darted from the thicket.