In electronics, xtal is an abbreviation for crystal, and refers to a piezoelectric crystal oscillator (a device containing quartz crystal which, if stimulated, will oscillate at a precise frequency and can be used to generate voltage sine waves). Frequently used in precise low-power clocks, and the generation of carrier radio frequencies.
An electronics simulation program, or an electronic diagram may describe a crystal oscillator as an xtal.

For example, "R1 = 1 kOhm, R2 = 500 Ohm, C1 = 10 nF, xtal1 = 4 Mhz"
by Bizork June 1, 2010
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