switch / swich/ • n. 1. a device for making and breaking the connection in an electric circuit: the guard hit a switch and the gate swung open. ∎  Comput. a program variable that activates or deactivates a certain function of a program.2. an act of adopting one policy or way of life, or choosing one type of item, in place of another; a change, esp. a radical one: his friends were surprised at his switch from newspaper owner to farmer.3. a slender flexible shoot cut from a tree.4. a junction of two railroad tracks, with a pair of linked tapering rails that can be moved laterally to allow a train to pass from one line to the other.5. a tress of false or detached hair tied at one end, used in hairdressing to supplement natural hair.• v. [tr.] 1. change the position, direction, or focus of: the company switched the boats to other routes. ∎  adopt (something different) in place of something else; change: she's managed to switch careers. ∎  [intr.] adopt a new policy, position, way of life, etc.: she worked as a librarian and then switched to journalism. ∎  substitute (two items) for each other; exchange: after ten minutes, listener and speaker switch roles.2. archaic beat or flick with or as if with a switch.PHRASAL VERBS: switch something off turn off an electrical device. ∎  (switch off) inf. cease to pay attention: as he waffles on, I switch off.switch something on turn on an electrical device.DERIVATIVES: switch·a·ble adj.