1. In a dishonourable manner or to a dishonourable degree
   "his grades were dishonourably low";
   - disgracefully, ingloriously, ignominiously, discreditably, shamefully, dishonorably [US]
    
2. With dishonour
   "he was dishonourably discharged";
   - dishonorably [US]
    
3. In a dishonourable manner
   "he acted dishonourably";
   - dishonorably [US]

See also: ignobly