noun

• (uncountable) Conduct that playfully causes petty annoyance.
  "Drink led to mischief."
• (countable) A playfully annoying action.
  "John's mischief, tying his shoelaces together, irked George at first."
• (collective) A group or a pack of rats.
  "Kirac, the leader of the rats under his charge, speaks to the major through his telepathic abilities that manifested after the alien virus infected him and his mischief of rats."
• (archaic) Harm or injury:
  "She had mischief in her heart."

verb

• (transitive, obsolete) To do a mischief to; to harm.
  ""Not now, Smee," Hook said darkly. "He is only one, and I want to mischief all the seven. Scatter and look for them.""
• (transitive, obsolete) To slander.
  "And so it hath been divers times; Men mischiefing the Jews to excuse their own Wickedness: as to instance one Precedent in the time of a certain King of Portugal."