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.
Source:
PAC, 2021, 93, 647. (Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)) on page 677 [Terms] [Paper]