dast ‧ ard ‧ ly /ˈdæstədli $ -ərd-/ BrE AmE adjective old-fashioned
[ Date: 1500-1600 ; Origin: dastard 'someone without courage, someone evil' (15-20 centuries) , perhaps from Old Norse dæstr ]
very cruel or evil:
tales of pirates and their dastardly deeds