Semi-spikes, or pseudo-spikes, are attack in the Super Smash Bros. series and Super Smash Flash 2 that send opponents at a horizontal trajectory and then a vertical trajectory. In between the horizontal and vertical trajectories in the games, a quarter circle trajectory occurs before the vertical trajectory, which gives time to input a command. This is what makes it different from a meteor smash and a regular spike. In Super Smash Flash 2, these moves send opponents in the same way.
Kirby crouches and quickly sticks out one of his legs forward. This move is a quick and powerful semi-spike.
Kirby spins around once on the ground with his feet sticking out to the sides of him. If the opponent touches his head or his underside, he or she will be sent upwards. If the opponent touches Kirby's feet, he or she will be semi-spiked.
Sheik does a quick swipe infront of herself. It semi-spikes along with having high base knockback and high knockback scaling. This makes it useful for gimping opponents with poor recoveries and making it an excellent KO move at high percentages.
Yoshi will crouch down and spin around hitting the opponent with his tail. Any opponent who is hit by the tail will be semi-spiked, but the attack has set knockback so it's useful for edgeguarding or getting the opponent away.