Spike

A spike is an attack in the  series and in Super Smash Flash that sends an enemy downwards. Unlike meteor smashes, spikes cannot be meteor cancelled, making them very powerful tools for edgeguarding.

In Super Smash Flash
Although the How to Play tutorial mentions meteor smashes, meteor cancelling is absent from Super Smash Flash. Therefore, the game only contains spikes.

Every character's can spike. Due to the instant-KO attack glitch, however, actually getting those moves to spike is considerably difficult; they will not move grounded opponents who are idling, and will strongly semi-spike opponents who are moving horizontally. In order to properly spike opponents, one needs to hit an airborne opponent who is not moving sideways at all.

In Super Smash Flash 2
In Super Smash Flash 2, meteor cancelling was added to the game in v0.8a of the demo, and, although there exists code to disable the mechanic for some attacks, such as 's tippered, the code does not actually work. Therefore, SSF2 only contains meteor smashes, and spikes are absent from the game.