pruning to decrease height and/or spread of a branch or crown.
Merriam-Webster Online Dictionary
reduction (noun)1.
the act or process of the state of being - reducing reduced
2.
a) something made by reducing
b) the amount by which something is reduced
3.
Spanish from Latin a South American Indian settlement directed by Jesuit missionaries
4.
- meiosis , specifically production of the gametic chromosome number in the first meiotic division
reduction (Wikipedia)