What is the meaning of Doubler?

One who doubles.

An instrument for augmenting a very small quantity of electricity, so as to render it manifest by sparks or the electroscope.

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.

Part of a distilling apparatus for intercepting the heavier fractions and returning them to be redistilled.

A blanket or felt placed between the fabric and the printing table or cylinder.

A person employed in a roller mill to fold the hot metal plates in half.

A device with two electrical plugs that plugs into an electrical outlet, effectively converting the electrical outlet into two; socket converter.

A diaper insert.

A tenement house having two families on each floor.

A biplane aeroplane or kite.

to double, duplicate

to double-cross

to overtake, pass

to dub

to repeat a school year

to line (a coat)

Source: wiktionary.org