adj. Having no excuse; not admitting of excuse or apology.
the GNU version of the Collaborative International Dictionary of English
adj. Having no excuse; not admitting of excuse or apology.
The Century Dictionary and Cyclopedia
Having no excuse.
Inexcusable.
Word Usage
"This excuseless /ju/ is perpetuated in Teach Yourself Ancient Greek 2002, Alan Henry and Gavin Betts - a couple of Australian academics, at Monash, which is my old university."