The Collaborative International Dictionary
Orthocenter \Or`tho*cen"ter\, n. [Ortho- + center.] (Geom.) That point in which the three perpendiculars let fall from the angles of a triangle upon the opposite sides, or the sides produced, mutually intersect.
Wiktionary
alt. (context geometry English): the intersection of the three lines that can be drawn flowing from the three corners of a triangle to a point along the opposite side where each line intersects that side at a 90 degree angle; in an acute triangle, it is inside the triangle; in an obtuse triangle, it is outside the triangle. n. (context geometry English): the intersection of the three lines that can be drawn flowing from the three corners of a triangle to a point along the opposite side where each line intersects that side at a 90 degree angle; in an acute triangle, it is inside the triangle; in an obtuse triangle, it is outside the triangle.
Usage examples of "orthocenter".
That is, that the orthocenter, centroid, and circumcenter of any triangle must lie in a straight line, with the centroid exactly twice as far from the orthocenter as from the circumcenter.