residuum
Concise Oxford English Dictionary © 2008 Oxford University Press:
residuum /rɪˈzɪdjʊəm/
▶noun (pl. residua /-djʊə/)
- 1 technical a chemical residue.
- 2 Sociology a class of society that is unemployed and without privileges or opportunities.
– origin C17: from L., neut. of residuus, residere ‘to remain’.
'residuum' also found in these Oxford entries:

