Definition - What does Trim mean?
To trim marijuana or cannabis plants is to cut or prune the plant in a way that produces more blooms and desirable crystals. The whole idea behind trimming a cannabis plant is to maximize the THC-producing parts of the plant and reduce the leaf or stem production.
Almost all marijuana is trimmed to some extent. Some varieties are naturally more compact, but others tend to want to grow leggier (branch out) and will need to be trimmed in order to control their growth.
Additionally, when the grower is ready to harvest, normally just after white hairs on the buds begin to turn red, the plants are carefully trimmed and extra branches removed.
Hydrolife explains Trim
Different varieties of cannabis are trimmed in different ways, depending very much on the structure of the plant. Some varieties are leafy, but the leaves are heavily covered in crystals. If the intended market is medicinal, the trimming needs to be adapted in order to keep some of the larger leaves, but trim out the smaller ones.
Trimming is also an essential part of the drying process. When the harvested plants begin to dry, whatever leaves remain will wrap around the bud and these leaves need to be cut away with a small scissors. The idea is to expose the flowering top that is covered in the buds and crystals, as these are the desirable parts of the plant.
For increased profitable, cannabis plants are trimmed to expose as many buds as possible. Although most trimming is done by hand with a scissors, there are commercial trimmers available for large-scale, commercial growers.