1) (of machinery, systems, objects etc) of, worked by, capable of producing, electricity (electric)

2) of, worked by, water or liquid moving through pipes (hydraulic)

3) a lever on a bicycle, sewing machine etc worked by the foot or feet (pedal)

4) worked or driven by compressed air; filled with compressed air (pneumatic)

5) (in history) a person who worked on the land and was sold with it like a slave (serf)

6) (to use) a pedal or lever that drives a machine (e.g. a sewing-machine) worked by pressure of the foot or feet (treadle)