1. A phaser is an electronic audio signal processor used to distort a signal by mixing a "dry", or unprocessed, signal with a copy of itself that has been filtered through an all-pass phase-shift network. As the filtered signal is mixed with the dry signal, the effect is that of a comb filter, notching out and reinforcing frequencies at fixed intervals up the frequency spectrum. When the all-pass filtered signal alone is heard at the output, the effect is commonly referred to as vibrato. In motion picture or television production, the effect is often used to imply that a sound originates from an artifical source (e.g. a computer or robot voice.)

2. A phaser is a fictional weapon most commonly used by personnel of the Federation in Star Trek. It emits a high-energy beam. According to the Star Trek Encyclopedia it stands for PHASed Energy Rectification. In the original scripts for Star Trek the energy weapons used by the crew were called 'Lasers'. However they were changed to Phaser before filming began, on the grounds that nobody was sure that lasers would not become commonplace in the next few years.

A phaser at its lowest setting, stuns a victim. This would be similar to the effect caused by a taser. At its highest setting, the phaser kills the victim. This is characterized by vaporization. The stun setting on phasers have little or no effect on certain species, forcing the user to set the phaser to "kill" which ranges from simple fatally burning a target to vaporization. Phasers can also be used to heat rock for a heat source when necessary and can also be adjusted for wide beam to simultaneously stun multiple targets.

Phasers can sometimes be set to overload. The exact procedure is unknown, but one can assume that some sort of feedback loop is established within the phaser mechanism. This causes the phaser to explode.

Other races have their own weapons. Romulans, for example, use disruptors.

3. Phaser is a trade name for makes of laser printer made by Xerox.