Definition of alum glass in English:

alum glass

noun

rare
  • 1historical A glassy form of alum produced especially by evaporating an aqueous solution (now historical).

  • 2A kind of glass containing alumina.

Origin

Late Middle English. Compare Anglo-Norman alum de glace, alun de glas, Middle French alun de glace, lit. ‘ice alum’ and also Anglo-Norman alomglas; compare further (after French) Middle Dutch aluun van glaetse.