undersampling

https://doi.org/10.1351/goldbook.08297

Sampling less frequently than is required by the Nyquist criterion.

Note:
Undersampling occurs when an analogue signal is digitized with less than two data points per wavelength of the shortest wavelength (highest wavenumber) radiation that reaches the detector.

See: folding in vibrational spectroscopy

Source:
PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 677 (https://doi.org/10.1515/pac-2019-0203)