Apical Dominance: A condition in plants where the stem apex prevents the development of lateral branches near the apex. It is controlled by auxins produced at the apical bud. Close to the bud, the auxin concentration is high and inhibits lateral growth; further back, the concentration is lower and branching occurs.*
Apical dominance is what gives Christmas trees their regular, tapered shape.
*Allaby, M. (2006). A dictionary of plant sciences (Revised ed.). Oxford: Oxford University Press.