motherboard

[muhth -er-bawrd, -bohrd] /ˈmʌð ərˌbɔrd, -ˌboʊrd/
noun, Computers.
1.
a rigid, slotted board upon which other boards that contain the basic circuitry of a computer or of a computer component can be mounted.
Compare board (def 14).
Origin
mother1 + board
British Dictionary definitions for motherboards

motherboard

/ˈmʌðəˌbɔːd/
noun
1.
(in an electronic system) a printed circuit board through which signals between all other boards are routed
motherboards in Science
motherboard
  (mŭ'ər-bôrd')   
The main circuit board of a computer, usually containing the central processing unit and main system memory as well as circuitry that controls the disk drives, keyboard, monitor, and other peripheral devices.