Glossary of American Football

I formation

A formation that includes a fullback and tailback lined up directly behind the quarterback while the quarterback is under center. By definition, the fullback lines up in front of the tailback. Several variations on this backfield formation exist, including the "Offset I" (in which the fullback lines up out of line to the left or right of the quarterback and halfback; also known as the strong or weak I depending on which direction the fullback is positioned), the "Maryland I" and "Power I" (in which an additional fullback is added to the backfield, either next to in the Power I's case or in front of in the Maryland I's case, the fullback).

icing the kicker

When a team calls time out just before the kicker has the ball snapped. A team is limited to calling one time-out on any given play (thus a team cannot repeatedly call all of its time-outs to prevent the game from continuing, or else a delay of game penalty or, more rarely, a palpably unfair act penalty is imposed). It is thought that kickers tend to miss after being iced due to nervousness, so icing the kicker usually happens at the end of the game before a walk-off field goal. Some kickers like Adam Vinatieri are famous for remaining accurate even after having been iced. There is evidence that this tactic doesn't work. (An older way of referring to this situation was "making the kicker think about it".)

illegal formation

On offense, there must be exactly seven players lined up on the line of scrimmage for at least one count before the ball is snapped. If not, then it is an illegal formation.

illegal motion

On offense, a player may be in motion but cannot be going forward at the time of the snap (except in Arena football where one player is allowed to do so), and a lineman must be set for one second before the snap. Otherwise it is an illegal motion.

illegal shift

On offense, only one person is allowed to be in pre-snap motion after the formation is set. A second person may go in motion after the first has come to a set position for one second. If these conditions are not met when sending people into motion, an illegal shift has occurred.

incomplete pass

A forward pass of the ball which no player legally caught.

inbounds lines

The hash marks.

indirect snap

A play in which the ball is handed to the quarterback rather than thrown directly to the ballcarrier by the center as in a direct snap play. So named because the quarterback acts as an intermediary in relaying the ball to the ballcarrier. Also used to refer to formations that use such a snap, as most modern formations do. Indirect snap formations exploded in popularity after World War II.

ineligible receiver

Certain players on the offense are not allowed to catch passes. For example, in most situations offensive interior linemen cannot be receivers and they may cause their team to be penalized if they catch the ball. An exception is if the ball has already been tipped by a different player. In six-man football all players are eligible receivers.

inside of a player's path

Relatively close (in reference to the sides of the field) to where the ball was snapped from. Thus, a ballcarrier's path in crossing the neutral zone may be said to be "inside" of an opponent, or an "inside run" in general, and a rushing defensive player may be said to put on an "inside move" or "inside rush".

inside of the movement of the ball between players

Directed toward a player who cuts between a player in the backfield who throws or hands the ball and the place from which it was snapped. Thus, an "inside pass" or "inside handoff". An "inside reverse" (sometimes called a scissors play) is a reverse play via an inside handoff.

intentional grounding

A type of illegal forward pass; thrown without an intended receiver and no chance of completion to any offensive player, for the sole purpose of conserving time or avoiding loss of yardage. This foul costs the offense a loss of down and 10 yards. If it occurs 10 yards behind the line of scrimmage, then the 10 yards is taken from the spot of the foul. If the foul is committed in the end zone the penalty is a safety. Intentional grounding is not called in the case of a spike after a hand to hand snap or if under NFL or NCAA rules, the quarterback was outside the tackle box, (the imaginary area between each tackle) at the time of the pass, provided that the ball travels at least to the line of scrimmage. The Tackle Box is also known as the Pocket. nfl rules

interception