WordWeb Online

1. Continuing forever without end
   "there are endlessly many possibilities"
   - infinitely
    
2. With unflagging resolve
   - ceaselessly, incessantly, unceasingly, unendingly, continuously, unremittingly
    
3. (spatial sense) without bounds
   "the Nubian desert seemed to stretch out before them endlessly"
    
4. All the time; seemingly without stopping
   "her nagging went on endlessly"
   - interminably

See also: endless

Encyclopedia: Endlessly