\Dou"bler\, n.
1. One who, or that which, doubles.

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

\Dou"bler\, n.
1. A part of a distilling apparatus for intercepting the
   heavier fractions and returning them to be redistilled.

2. (Calico Printing) A blanket or felt placed between the
   fabric and the printing table or cylinder.