verb

• (transitive) To agitate rapidly and repetitively, or to stir with a rowing or rocking motion; generally applies to liquids, notably cream.
  "Now the cream is churned to make butter."
• (transitive, figuratively) To produce excessive and sometimes undesirable or unproductive activity or motion.
  "The slope of the terrain, shaped like a funnel, squeezed the growing swell of churning snow into a steep, twisting gorge."
• (intransitive) To move rapidly and repetitively with a rocking motion; to tumble, mix or shake.
  "I was so nervous that my stomach was churning."
• (business, of a customer) To stop using a company's product or service.
  "Subscriptions can be ended or canceled, which is known as churn. If there are no subscriptions, a customer churns when they stop using the product."

noun

• (business, uncountable) Customer attrition; the phenomenon or rate of customers leaving a company.
• (telecommunications) The time when a consumer switches his/her service provider.
• (telecommunications) The mass of people who are ready to switch carriers.
• (historical) The last grain cut at harvest; kern.