Shielding is a technique that is performed when the player holds the shield button down, and a bubble of energy surrounds the character. Shielding renders the character invincible to all attacks except grabs and Final Smashes. A way to solve this problem is to sidestep before the enemy grabs the character. While the character shields, the bubble shrinks. Some special moves work similarly to shielding, such as Ness' PSI Magnet and Lloyd's Guardian (in early versions). If the player holds down the shield button for too long, or if the opponent hits the shield enough to destroy the shield, the character will be stunned for a short period of time, but if the opponent attacks that player, it goes back to normal.
Yoshi has a unique shield that works differently in comparison to the normal shield. Instead of a bubble, he completely surrounds himself in an egg. The egg does not shrink, but instead darkens from white to dark red. Due to this property, Yoshi is immune to shield stabbing, as his shield will always completely envelop him. Yoshi is able to jump out of his shield in Super Smash Flash 2 like he can in Super Smash Bros. and Super Smash Bros. for Nintendo 3DS and Wii U.
Jigglypuff has a large shield compared to her body, which shrinks at a slower rate than the other characters'. However, if her shield is broken, the force of the knockback will send Jigglypuff soaring into the air and, without a ceiling, cause her to be Star KO'ed. This is known as a Shield Jump.
A shield stab, also known as a shield poke, is the event of finding a damageable portion of a character slightly outside of their shield and striking it bypassing their attempt to shield. This is a useful technique because it can used to strike an otherwise defended enemy.
Some characters are easier to shield stab then others. Captain Falcon or Samus is too tall for a spherical bubble to cover properly. While characters who are to short or round such as Kirby and Jigglypuff are hard to shield stab for similar reasons.
Some moves are suited for shield stabbing than others. Multi-hit moves like the Mach Tornado when used at their maximum range can deplete a shield with the first few hits and then hit the opponent on the next few. The hitbox shape of a move also affects its shield stabbing viability; Meta Knight's down tilt hits very low to the ground, it could hit the opponent's uncovered feet without touching their shield center.
As mentioned above due Yoshi's unique shield he cannot be normally shield stabbed.
A Shield Grab is the act of grabbing while shielding. It is used to punish attacks when they are blocked because the attacker will be caught in the lag of their attacks and the defender's grab can connect with little trouble. Shield grabs allow a character to get around the delay of dropping the shield.
Due to grabbing input-wise is the same as shielding and attacking at the same time, shield grabs can also be done just by pushing the attack button, instead of pressing the grab button.
Shield jump is an aspect of ever character's shield. When a character's shield is broken they will be knocked into the air. However, for most characters this is not truly a problem. However, as mentioned above when Jigglypuff's shield is broken, she will sent up with enough knockback to Star KO herself.
Dashing shield is a technique that is preformed by shielding during a run (not in the initial dash animation) which makes the shield slide a short distance. Sliding versions of out-of-shield techniques can come from this, such as dashing shield grab. Dashing shield can work similarly to a dash cancel.
Shield stun is the effect a character experiences when their shield is hit and they begin to slide. During this time the shielding player won't be able to do anything. This becomes a problem when the opponent consistently hits a players shield creating shield pressure. The shielded player won't be able to react and prevent the opponent from breaking his/her shield.
Shield stun formula
Attack Damage = amount of damage dealt after charge is applied
Shield Stun Multiplier = custom multiplier for attacks that defaults to 1.0
Round ((4.45 + attackDamage) / 2.235 / 2 * shieldStunMultiplier * 1.5)