Monopodial: Having a single axis of growth with lateral branching occurring on either side of the main axis, most commonly used to describe the growth of inflorescences but also to describe vegetative growth, such as in some orchids.*
Phalaenopsis, or moth orchid, in the centre of the photo is showing monopodial growth. It produces leaves and flowers along the sides of a single stem, with new leaves always growing from the apex (end) of the stem.
*Pell, S.K., Angell, B. (2016). A botanist’s vocabulary: 1300 terms explained and illustrated. Portland: Timber Press.