trimmer

noun

1.
a worker who thins out and trims trees and shrubs
pruner
Derived from:
trim
2.
a machine that trims timber
Derived from:
trim
3.
capacitor having variable capacitance; used for making fine adjustments
trimming capacitor
4.
joist that receives the end of a header in floor or roof framing in order to leave an opening for a staircase or chimney etc.
trimmer joist