Collateral assurance, that which is made, over and above the deed itself. Collateral circulation (Med. & Physiol.), circulation established through indirect or subordinate branches when the supply through the main vessel is obstructed. Collateral issue. (Law) (a) An issue taken upon a matter aside from the merits of the case. (b) An issue raised by a criminal convict who pleads any matter allowed by law in bar of execution, as pardon, diversity of person, etc. (c) A point raised, on cross-examination, aside from the issue fixed by the pleadings, as to which the answer of the witness, when given, cannot subsequently be contradicted by the party asking the question. Collateral security, security for the performance of covenants, or the payment of money, besides the principal security,