A way for a holder of property to initiate a suit between two or more claimants to the property.  If, for example, A holds property that he knows he does not own, but that both B and C are claiming, A can sue both B and C in an interpleader action, where B and C could litigate who actually owns the property.  Interpleader avoids the problem of A being sued separately by both B and C, and potentially losing the same piece of property twice.