Source : WordNet®

keep back
     v 1: keep under control; keep in check; "suppress a smile"; "Keep
          your temper"; "keep your cool" [syn: {restrain}, {suppress},
           {keep}, {hold back}]
     2: secure and keep for possible future use or application; "The
        landlord retained the security deposit"; "I reserve the
        right to disagree" [syn: {retain}, {hold}, {hold back}]
     3: hold back; refuse to hand over or share; "The father is
        withholding the allowance until the son cleans his room"
        [syn: {withhold}]