Coincident with a tangent at the circumference of a tree or log, or parallel to such a tangent. In practice, it often means roughly coincident with a growth ring Found on http://www.encyclo.co.uk/local/21113
Tan·gen'tial adjective (Geom.) Of or pertaining to a tangent; in the direction of a tangent. Tangential force (Mech.) , a force which acts on a moving body in the direction of a tangent to the path of the body, its effect being to increase or diminish the velocity; -- distingu... Found on http://www.encyclo.co.uk/webster/T/9