adj. 1. (of a relation) having the property that if the relation holds between a first object and a second, and between the second and a third, then it holds between the first and the third; for example,... is greater than... is transitive, since for any a, b, and c, if a > b and b > c then a > c. Compare intransitive, non-transitive. See also equivalence relation. 2. (of a graph) such that the adjacency relation on the vertices is transitive. See adjacent. 3. (of an action of a group on a non-empty set) such that the set has precisely one orbit.