doubler

noun10

1. •
   One who doubles.
2. •
   A person employed in a roller mill to fold the hot metal plates in half.
3. •
   A device with two electrical plugs that plugs into an electrical outlet, effectively converting the electrical outlet into two; socket converter.
4. •
   A metal plate riveted or welded over a preexisting metal structural component to reinforce it and relieve the stress on the preexisting component, or to serve as a patch where part of the original structure has failed or been removed.

   • The mechanics fastened a doubler over the hole where the cracked section of the plane's skin had been cut out.
   • The airworthiness directive called for riveting a reinforcing doubler to the wing midspar web to keep the spar from buckling under flight loads.
5. •
   A diaper insert.
6. •
   (informal) A biplane aeroplane or kite.
7. •
   An instrument for augmenting a very small quantity of electricity, so as to render it manifest by sparks or the electroscope.
8. •
   Part of a distilling apparatus for intercepting the heavier fractions and returning them to be redistilled.
9. •
   A blanket or felt placed between the fabric and the printing table or cylinder.
10. •
    (dialect, US) A tenement house having two families on each floor.