Head: head is a commonly used synonym for search coil.
Masking: masking occurs when ground minerals or buried objects interfere with the detection of a legitimate find, resulting in a mixed signal. This is also called "nulled out."
Matrix: matrix refers to the total detection area covered by a search coil's electromagnetic field. (Though if you ever say "What is the matrix?," don't blame us if you wake up and find yourself talking to Laurence Fishburne.)
Negative Ground: if a metal detector has a preset ground balance, then negative ground, i.e. ground that has more non-conductive minerals and fewer conductive minerals, will cause a negative or nulling effect. In other words, negative ground may cause metal detectors to ignore more signal than is necessary.
Neutral Ground: neutral ground is soil that contains neither conductive nor non-conductive minerals.
Notch: notch filtering or notch discrimination is used to create a range of accepted and rejected targets. Setting the notch level to discriminate against certain objects means tuning out or blocking a particular frequency band. This is called notch reject. Conversely, creating a notch window of accepted frequencies is called notch accept.
Null: when a metal or coin detector coil passes over targets that have been discriminated against or are outside of the accepted notch window, a detector's threshold audio will go quiet or drop momentarily, i.e. go null.
Pinpointing: pinpointing refers to the act of determining the precise location of a target. This can be accomplished by manually "detuning" a metal detector, or adjusting it to be less sensitive, and then sweeping the target response area again. Because the detector is less sensitive after detuning, an audio signal should provide a more exact location due to the strength of the signal.
Positive Ground: positive ground is soil that contains a high amount of conductive minerals. Positive ground results in too many signals, which can make it difficult or impossible for a metal detectorist to find legitimate targets. This often occurs on wet beaches, due to their high salt content.
Prospecting: prospecting means treasure hunting or going metal detecting in search of gold, silver, or valuables.