Definition of malt-culms in US English:

malt-culms

noun

British Regional
  • Treated as plural. In the process of malting: the radicles and acrospires of grain that has been partly germinated and kiln-dried, which are separated from the malt. Also (rarely) collectively, in singular form.

Origin

Late Middle English; earliest use found in Promptorium Parvulorum. From malt + the plural of culm.