The phaser adapter was an anti-Borg modification chip added to phasers used by Starfleet in 2367. (TNG: "The Best of Both Worlds, Part II")

In 2366, it was discovered that Borg systems were vulnerable to phaser blasts on a resonance frequency spread in the high narrow band. The Borg adapted to compensate for this weakness after Captain Jean-Luc Picard was assimilated as the Locutus. (TNG: "The Best of Both Worlds") In 2367, based on a suggestion from Wesley Crusher, a chip known as the phaser adapter was designed. It would automatically re-tune phasers to a random setting after each discharge. Using the adapter, phasers were set on a rotating modulation, to allow at most twelve shots to penetrate Borg shielding before they adapted. (TNG: "The Best of Both Worlds, Part II"; Star Trek: First Contact; VOY: "Scorpion")

A similar technology was invented in 2375 by Species 10026. The Borg adapted by triaxilating their deflector shield geometry to absorb the energy of the modulating phaser pulses. (VOY: "Dark Frontier")