Contras

noun

1. A deal to swap goods or services.
2. A conservative; originally tied to Nicaraguan counter-revolutionaries.
3. An entry (or account) that cancels another entry (or account).

   "The sum for each contra account is shown in the last column."

4. Any of the musical instruments in the contrabass range, e.g. contrabassoon, contrabass clarinet or, especially, double bass.
5. A contra dance.