noun one who, or that which, doubles.
2. doubler ·add. ·noun a blanket or felt placed between the fabric and the printing table or cylinder.
3. doubler ·noun an instrument for augmenting a very small quantity of electricity, so as to render it manifest by sparks or the electroscope.
4. doubler ·add. ·noun a part of a distilling apparatus for intercepting the heavier fractions and returning them to be redistilled.