I.out [美 aʊt, 英 aʊt]副out often appears as the second element of certain verb structures in English (come out, keep out, knock out, etc). For translations, see the relevant verb entry (come, keep, knock, etc).
As hard as they tried, the occupants of the castle could not scrub out the stains, and so were forced to cover the steps in wood panelling, which remains today.