As a Noun: 1. Two things that are the same size and shape and are intended to be used together. English = pair. As a Verb or Adjective: 1. Of something, to become twice as large as it was before. English = double. 2. Of something, to be twice its normal size. English = (be) double. 3. Of something, to consist of two things of the same kind or to be something, for example a bed, that is intended to be used by two people. English = (be) double.