Situated at the side: belonging to the side or to what is at the side; hence, occupying a secondary or subordinate position.Acting indirectly; acting through side channels.Accompanying; attendant, especially as an auxiliary; aiding, strengthening, confirming, etc., in a secondary or subordinate way: as, collateral aid; collateral security (see below); collateral evidence.Descending from the same stock or ancestor (commonly male) as another, but in a different line: distinguished from lineal.In botany, standing side by side: as, collateral ovules.In geometry, having a common edge, as two adjoining faces of a polyhedron.n. A kinsman or relative descended from a common ancestor, but not in direct line.n. Anything of value, or representing value, as bonds, deeds, etc., pledged as security in addition to a direct obligation.