WordWeb Online

1. By a factor of two
   "the price increased twofold last year";
   - two times

1. Having more than one decidedly dissimilar aspects or qualities
   "a twofold role for an actor"; "the office of a clergyman is twofold; public preaching and private influence";
   - double, dual, two-fold, treble, threefold, three-fold, trifold
    
2. Twice as great or many
   "a twofold increase";
   - double, doubled, two-fold, bifold

See also: multiple