A glitch is a problem or malfunction, usually a temporary one, in a system or machine. Your science fair team might experience a major glitch in your plans if you lose your data tables as the result of a computer glitch.
Glitch is a pretty new word, introduced in the 1960s when the science and technology of space flight was being developed. It originally meant a sudden surge of electrical current that caused a disturbance or malfunction. The word can also be used more broadly to describe any unexpected difficultly, like the glitch in your travel plans that resulted from airport delays.