v. Simple past tense and past participle of double.
the GNU version of the Collaborative International Dictionary of English
adj. rendered twice as great or twice as many.
adj. folded in two.
The Century Dictionary and Cyclopedia
Made double; duplicated.
In music, reinforced by its octave: said of a tone in a melody or a chord.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. twice as great or many
Word Usage
"For example, in this study, they are including people who are what they call doubled up, meaning you had problems with your home, you moved in with a sister or you lived with your parents, and you have children there."