means Practicing combat with a partner using restrained, deliberate blows — fighting to learn rather than to win.

from From the verb 'spar,' which originally described gamecocks striking with their legs and spurs before it was borrowed for boxers. That 'spar' is of uncertain origin, possibly related to an Old English or Old French word for striking or thrusting, and quite separate from the 'spar' meaning a wooden pole. By the 18th century it had moved from the cockpit to the boxing ring, where two fighters could trade blows in earnest practice without true enmity.