Collateral  —n. 1 security pledged as a guarantee for the repayment of a loan. 2 person having the same ancestor as another but by a different line. —adj. 1 descended from the same ancestor but by a different line. 2 side by side; parallel. 3 a additional but subordinate. B contributory. C connected but aside from the main subject, course, etc.  collaterally adv. [latin: related to *lateral]