Definitions for: Dastardly

[adj] treacherously cowardly; "the unprovoked and dastardly attack by Japan on...December 7th"- F.D. Roosevelt

Webster (1913) Definition: Das"tard*ly, a.
Meanly timid; cowardly; base; as, a dastardly outrage.

Synonyms: coward(a), cowardly, dastard(a), fearful