Phase pulses were the concentrated phase-modulated energy discharges produced by some types of phase weapons.
Phase-pistols used by the MACO fired phase pulses. A pulse could be set for stun or kill. In 2154, Talas was shot with a MACO phase-pistol set to kill. Although she was only grazed, being an Andorian she was especially susceptible to phase-pulse infections, and subsequently died of her injuries. (ENT: "Babel One")
Particle rifles used by the MACO fired similar discharges. The MACO pistol was called a plasma gun [1](X) and identified as an EM-33 gun [2](X) in the It's A Wrap! sale and auction on eBay. This suggests that the phase pulse might be a type of plasma bullet.