adj.
  - happening quickly or promptly.
- moving or capable of moving at high speed.
adv.
 literary except in combination swiftly:
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 a swift-acting poison.
n.
   - a fast-flying insectivorous bird with long, slender wings, spending most of its life on the wing. 
[Apus apus (Eurasia) and other species, family Apodidae.]
- a moth, typically yellow-brown, with fast darting flight. 
[Family Hepialidae.]
- a light adjustable reel for holding a skein of silk or wool.
Derivative
  
    - swiftly adv.
- swiftness n.
 
  Etymology
  OE, from the Gmc base of OE swīfan ‘move in a course, sweep’.