A slant route in football is a pass route in which a receiver takes a few steps forward then cuts towards the middle of the field sharply at a 45 degree angle. The cut is usually made after three steps around five yards past the line of scrimmage. It may also be beneficial to envision a slant as a shorter version of a post.
Slant routes are the quintessence of the short pass game. They are great plays to run at the start of a set of downs to pick up quick yardage or on a third and short scenario to try and pick up the first down. When a quarterback is under center, they will take a three-step drop and throw the pass hard and fast right to their open receiver. From a shotgun, the quarterback only takes a one-step drop. Because this route is so fast, it often demands the quarterback make an informed decision on where to throw before the snap occurs. This route is great for capitalizing on defenses where the defender plays off, 5-7 yards deep past the line of scrimmage. Additionally, it perfectly exploits the gap between the corner and safety in a cover 2 defense.
Covering slant routes can be a nightmare for defenses. A good receiver will bob and chop before their cut to try and mislead a defender, because all they need is a moment of separation to be open and catch the ball. Slant routes are best defended by man up defense, where a defender plays man and lines up only a yard away from the receiver. The key is taking away the inside arm of the receiver, because this is the aiming point for the quarterback on a slant route. However, some defenses will be hesitant to play a man defense in a situation where the corner is outmatched by their receiver or where there is more distance to attain a first down. For example, when an offense runs a slant route on 1st and 10, the defense may opt for a zone play. At this point, the receiver will have a window between defenders, and the defensive strategy then relies on a linebacker making an outstanding play, or simply minimizing yards after the catch.