spurious emission

This term is defined in ECSS-E-ST-50-05C Rev. 2 as
emissions on a frequency, or frequencies, which are outside ±2,5 times the occupied bandwidth and the level of which may be reduced without affecting the corresponding transmission of information

This term is defined in ECSS-E-ST-20-07C Rev. 1 as
electromagnetic emission from the intended output terminal of an electronic device, but outside of the designed emission bandwidth