A line in a survey which, being accurately determined in length and position, serves as the origin from which to compute the distances and positions of any points or objects connected with it by a system of triangles.
Verb
(transitive) To give as its foundation or starting point; to lay the foundation of.
(transitive) To be located (at a particular place).
(acrobatics, cheerleading) To act as a base; to be the person supporting the flyer.