x1 (linear manifold, vector, etc.) is/lies secant to x2 (object, surface, curve, manifold, etc.) passing through or toward points/loci x3 (set of intersected points), by standard/definition/in system x4.
No necessary implication of co-directionality. No implication about nontriviality (id est: possibly includes diameters/radii or tangents). Prone to mathematical/geometric generalization. It can be used metaphorically as in English ("secantial") for a line of discussion (x1) which relates to or touches the general topic or discussion (x2) in a non-distant manner or in several ways or at multiple points (more intimately than "tangential" implies, but still as sidetrack/a bit off-topic), the latter acting as the primary/main/current/relevant/focal topic or discussion, due to or at a connecting points/details/particular subtopics/ideas (x3), with x1 being a somewhat relevant or interesting branching line of thought other than the main one; in this case, it is understood in sensu stricto (nontrivially/strictly/properly/praperi secant). See also: panra, kukru, mijgresirji; tanjo, zo'anjo; ta'o; pagre.