Demote

Demote (v)
to reduce to a lower grade or rank

Andrew's boss was so angry with him for coming late to work every day that Andrew was demoted from his position as manager to janitor. He was so embarrassed by being reduced to a custodian that he begged his boss to promote him back to manager. Kevin promised his boss that he would never be late to work again. Unfortunately, his boss didn't believe him and Kevin remained demoted. In my opinion, Kevin's boss demotes people so often that most of the employees have given up trying to succeed.

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