adj.1. Situated or running side by side; parallel.
2. Coinciding in tendency or effect; concomitant or accompanying.
3. Serving to support or corroborate: collateral evidence.
4. Of a secondary nature; subordinate: collateral target damage from a bombing run.
5. Of, relating to, or guaranteed by a security pledged against the performance of an obligation: a collateral loan.
6. Having an ancestor in common but descended from a different line.