This is an atom, radical, molecule or molecular moiety which has lost one of more electrons thereby attaining an electrically positive charge. The use of the term cation as an alternative is not recommended. The use of mass ion is not recommended.
See: negative ion (in mass spectrometry)
Source:
PAC, 1991, 63, 1541. 'Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)' on page 1549 (https://doi.org/10.1351/pac199163101541)