English Noun jack-a-dandy (plural jack-a-dandies) (archaic) A little, young, or worthless dandy. Synonyms: dude, fopling; see also Thesaurus:dandy (archaic) A little or young foppish or rude person. (New Zealand) A small patch of light reflected from a shiny surface onto another surface such as a wall or ceiling. References “jack-a-dandy”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC. Wikiwand - on Seamless Wikipedia browsing. On steroids.