noun

• (uncountable) A cheerful attitude; happiness; a good, happy, or positive mood.
  "I have not that alacrity of spirit, / Nor cheer of mind, that I was wont to have."
• (now uncountable) That which promotes good spirits or cheerfulness, especially food and entertainment prepared for a festive occasion.
  "a table loaded with good cheer"
• (countable) A cry expressing joy, approval or support, such as "hurrah".
  "Three cheers for the birthday boy!"
• (countable) A chant made in support of a team at a sports event.

verb

• (transitive) To gladden; to make cheerful; often with up.
  "We were cheered by the offer of a cup of tea."
• (transitive) To infuse life, courage, animation, or hope, into; to inspirit; to solace or comfort.
  "The proud he tam'd, the penitent he cheer'd."
• (transitive, obsolete) To encourage to do something.
  "Let’s cheere our ſouldiers to incounter him, […] And burne him in the fury of that flame, That none can quench but blood and Empery."
• (ambitransitive) To applaud or encourage with cheers or shouts.
  "The crowd cheered in support of the athletes."

noun

• (chiefly Canada, US) Cheerleading, especially when practiced as a competitive sport.
  "Alex participated in cheer all four years of college."