What is the meaning of keep back?

verb

• Keep under control; keep in check.
  • usage: "suppress a smile"; "Keep your temper"; "keep your cool"
  • synonyms: restrain, keep, hold back
• Secure and keep for possible future use or application.
  • usage: "The landlord retained the security deposit"; "I reserve the right to disagree"
  • synonyms: retain, hold, hold back
• Hold back; refuse to hand over or share.
  • usage: "The father is withholding the allowance until the son cleans his room"
  • synonyms: withhold