In the National Football League, an illegal procedure is used to refer to a number of different penalties.
Types of illegal procedure
Some penalties are signalled with a generic "illegal procedure" signal. Examples are: False start Illegal formation Kickoff or safety kick out of bounds Player voluntarily going out of bounds and returning to the field of play on a punt
Some examples of similar penalties have their own signals. Examples include: Illegal shift Illegal motion Illegal forward pass Illegal touching of a forward pass Ineligible receiver downfield Illegal substitution
Usage at different levels
It is used similarly to the professional level at the high school level, but this term is not referenced at all in the collegiate rule book.