Original: An oscilloscope (abbreviated sometimes as scope or O-scope) is a type of electronic test instrument that allows signal voltages to be viewed, usually as a two-dimensional graph of one or more electrical potential differences (vertical axis) plotted as a function of time or of some other voltage (horizontal axis).
Simplified: An oscilloscope (sometimes abbreviated CRO, for cathode-ray oscilloscope, or commonly just scope or O-scope) is a piece of electronic test equipment that allows signal voltages to be viewed. Usually it shows a two-dimensional graph of one or more electrical potential differences (vertical axis). These are plotted as a function of time or of some other voltage (horizontal axis).