a. [ LL. collateralis; col- + lateralis lateral. See Lateral. ] 1. Coming from, being on, or directed toward, the side; as, collateral pressure. “Collateral light.” Shak. [ 1913 Webster ]

2. Acting in an indirect way. [ 1913 Webster ]

If by direct or by collateral hand
They find us touched, we will our kingdom give . . .
To you in satisfaction. Shak. [ 1913 Webster ]

3. Related to, but not strictly a part of, the main thing or matter under consideration; hence, subordinate; not chief or principal; as, collateral interest; collateral issues. [ 1913 Webster ]

That he [ Attebury ] was altogether in the wrong on the main question, and on all the collateral questions springing out of it, . . . is true. Macaulay. [ 1913 Webster ]

4. Tending toward the same conclusion or result as something else; additional; as, collateral evidence. [ 1913 Webster ]

Yet the attempt may give
Collateral interest to this homely tale. Wordsworth. [ 1913 Webster ]

5. (Genealogy) Descending from the same stock or ancestor, but not in the same line or branch or one from the other; -- opposed to lineal. [ 1913 Webster ]

☞ Lineal descendants proceed one from another in a direct line; collateral relations spring from a common ancestor, but from different branches of that common stirps or stock. Thus the children of brothers are collateral relations, having different fathers, but a common grandfather. Blackstone. [ 1913 Webster ]

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. --
collateral damage, (Mil.) damage caused by a military operation, such as a bombing, to objects or persons not themselves the intended target of the attack. [ 1913 Webster +PJC ]

n. 1. A collateral relative. Ayliffe. [ 1913 Webster ]

2. Collateral security; that which is pledged or deposited as collateral security. [ 1913 Webster ]

adv. 1. Side by side; by the side. [ 1913 Webster ]

These pulleys . . . placed collaterally. Bp. Wilkins. [ 1913 Webster ]

2. In an indirect or subordinate manner; indirectly. [ 1913 Webster ]

The will hath force upon the conscience collaterally and indirectly. Jer. Taylor. [ 1913 Webster ]

3. In collateral relation; not lineally. [ 1913 Webster ]

n. The state of being collateral. [ 1913 Webster ]