1. Continuing forever without end
   - 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

• unbeneficed
• unbent
• unbiased
• unbiassed
• unbidden
• unbigoted
• unbind
• unbitter
• unbleached
• unblemished
• unblended
• unblessed
• unblinking
• unblinkingly
• unblock
• unbloody
• unblushing
• unblushingly
• unbodied
• unbolt
• unbolted
• unbooked
• unbordered
• unborn
• unbosom