Counters

A deal to swap goods or services.

A conservative; originally tied to Nicaraguan counter-revolutionaries.

An entry (or account) that cancels another entry (or account).

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

Any of the musical instruments in the contrabass range, e.g. contrabassoon, contrabass clarinet or, especially, double bass.

One who counts

"He's only 16 months, but is already a good counter – he can count to 100."

A reckoner; someone who collects data by counting; an enumerator.

An object (now especially a small disc) used in counting or keeping count, or as a marker in games, etc.

"He rolled a six on the dice, so moved his counter forward six spaces."

A telltale; a contrivance attached to an engine, printing press, or other machine, for the purpose of counting the revolutions or the pulsations.

Something opposite or contrary to something else.

A proactive defensive hold or move in reaction to a hold or move by one's opponent.

"Always know a counter to any hold you try against your opponent."

The overhanging stern of a vessel above the waterline, below and somewhat forward of the stern proper.

The piece of a shoe or a boot around the heel of the foot (above the heel of the shoe/boot).

To contradict, oppose.

To return a blow while receiving one, as in boxing.

To take action in response to; to respond.

To encounter.