Given a power spectrum (a plot of power vs. frequency), aliasing is a false translation of power falling in some frequency range 
outside the range. Aliasing is caused by discrete
sampling below the Nyquist frequency. It can
be minimized by either increasing the underlying sampling rate or (if that is not
practical or possible) pre-filtering the signal to suppress high-frequency components.
Aliasing
See also
Antialiasing, Discrete Fourier Transform, Fast Fourier Transform, Leakage, Nyquist FrequencyExplore with Wolfram|Alpha
References
Blackman, R. B. and Tukey, J. W. "Aliasing" §12 in The Measurement of Power Spectra, From the Point of View of Communications Engineering. New York: Dover, pp. 31-33, 1959.Roberts, S. §in Lecture 7-The Discrete Fourier Transform. http://www.robots.ox.ac.uk/~sjrob/Teaching/SP/l7.pdf.Referenced on Wolfram|Alpha
AliasingCite this as:
Weisstein, Eric W. "Aliasing." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Aliasing.html