Letters that make plug-in
g, l, n, p, i, u are letters that make 'plug-in'
1 possible definitions for 'plug-in'
Under this definition, plug-in is a noun and has the following properties:
circuit board, circuit card, add-in, card, board have the same meaning as 'plug-in'
'plug-in' can be a type of printed circuit.
CPU board, mother board, PC board are types of 'plug-in'.