Definition of downmost in English:

downmost

adverb & adjective

British
  • The furthest down; at or towards the bottom.

    • ‘If the cuticle was downmost, the water dispersed immediately across the section.’
    • ‘Lay the machine on its side with the pump downmost and remove sump and look in pump for obstruction.’

Pronunciation

downmost

/ˈdaʊnməʊst/