1. [noun] One who doubles.
2. [noun] An instrument for augmenting a very small quantity of electricity, so as to render it manifest by sparks or the electroscope.
3. [noun] (US) (dialect) A tenement house having two families on each floor.
4. [noun] (colloquial) A biplane aeroplane or kite.
5. [noun] Part of a distilling apparatus for intercepting the heavier fractions and returning them to be redistilled.
6. [noun] (calico printing) A blanket or felt placed between the fabric and the printing table or cylinder.
7. [noun] An electronic device that doubles the voltage or the frequency of an input signal.
