1 British English
to officially force someone with a mental illness to go to a psychiatric hospital, because they are dangerous to themselves or other people
to separate something into parts:
Peel and section the oranges.
3 technical or medical
to cut a very thin flat piece from skin, a plant etc so that you can look at it under a microscope
to cut a part of the body in a medical operation
section something ↔ offphrasal verb
The vegetable plots were sectioned off by a low wall.