master, power
The master switch is under the stairs.

electric, electrical
off, on, on-off
I couldn't find the off switch on the remote control.

dimmer, timer (esp. BrE), toggle (esp. AmE)
We fitted dimmer switches in all the bedrooms.

ignition, light, wall (AmE)

flick, flip, hit, press, pull, throw, turn off, turn on
Someone threw a switch and the electricity went off.

activate sth, control sth, operate sth
This switch controls the heating system.

by a switch
The light operates by a timer switch.

on a switch
The heater is on a timer switch.

switch for
the switch for the air conditioning

at the flick of a switch
in the days before electricity was available at the flick of a switch

abrupt, sudden
big
complete
tactical (esp. BrE)
The team's manager made a shrewd tactical switch.

make

switch away from, switch from
There will be no overnight switch away from old voting habits.
her switch from full-time to part-time work

switch back to, switch over to, switch to
He's a classical singer who has made the switch over to pop.

switch between
the recent switches between direct and indirect taxation

switch in
their abrupt switch in allegiance