A demand made in a PLEADING against another party on the same side of the lawsuit.
For example, a manufacturer of desks shipped thirty desks to a buyer by truck. When the buyer refused to pay because the desks arrived in a damaged condition, the manufacturer sued both the buyer and the trucking company. The buyer did not know whether the manufacturer or the trucking company was responsible for the damage, so the buyer served an answer containing a denial that he owed money to the manufacturer for unusable desks and a cross-claim demanding that the trucking company compensate him for the damage to the desks.
A counterclaim is comparable to a cross-claim except that it is a claim against an adverse party in the lawsuit, not a party on the same side of the lawsuit.