Source : Webster's Revised Unabridged Dictionary (1913)

Discreditable \Dis*cred"it*a*ble\, a.
   Not creditable; injurious to reputation; disgraceful;
   disreputable. -- {Dis*cred"it*a*bly}, adv.

Source : WordNet®

discreditably
     adv : in a dishonorably manner or to a dishonorable degree; "his
           grades were disgracefully low" [syn: {disgracefully}, {ingloriously},
            {ignominiously}, {shamefully}, {dishonorably}, {dishonourably}]