viroid viroid /ˈvaɪrɔɪd/

noun

1. The smallest of viruses; a plant virus with its RNA arranged in a circular chromosome without a protein coat  ( viroid , virusoid )
   the smallest of viruses; a plant virus with its RNA arranged in a circular chromosome without a protein coat
   
   

 feather feather /ˈfɛðɝ/

noun

1. () The light horny waterproof structure forming the external covering of birds  ( plumage , plume , feather )
   the light horny waterproof structure forming the external covering of birds
    The feather of a bird is a remarkable thing, lightweight and flexible, yet strong enough to provide lift and insulation
   The feather of a bird is a remarkable thing, lightweight and flexible, yet strong enough to provide lift and insulation
   
   
2. Turning an oar parallel to the water between pulls  ( feather , feathering )
   turning an oar parallel to the water between pulls
   

verb

1. () Join tongue and groove, in carpentry  ( feather )
   join tongue and groove, in carpentry
   
2. Grow feathers  ( feather , fledge )
   grow feathers
    The young sparrows are fledging already
   The young sparrows are fledging already
   
3. Turn the oar, while rowing  ( feather , square )
   turn the oar, while rowing
   
4. Turn the paddle; in canoeing  ( feather , square )
   turn the paddle; in canoeing
   
5. Cover or fit with feathers  ( feather )
   cover or fit with feathers
   

 swing door swing door /ˈswɪŋ dɔːr/

noun

1. A door that swings on a double hinge; opens in either direction  ( swing door , swinging door [ N. American] )
   a door that swings on a double hinge; opens in either direction
   
   

 defense system defense system /dɪˈfɛns ˈsɪstəm/

noun

1. [American] The weaponry available for the defense of a region  ( defence system [Canadian, British] , defense system [American] )
   the weaponry available for the defense of a region