bigtime adjective 1adverb 1forms 3 adjective1 •Of major significance or importance.Wait till you see your name in two-foot electrics over the front of every big-time house in the country. — 1918 adverb1 •(informal, figurative) To a significant degree.This was the first test for that message -- and it failed bigtime. — 2018 formsbigtimes · more bigtime · most bigtime