flat–out 
/ˈflætˌaʊt/ adjective
always used before a noun /ˈflætˌaʊt/ adjective informal 1 chiefly US : absolute and complete
▪ It was a flat-out lie. ▪ a flat-out refusal 2 : greatest possible : maximum
▪ a flat-out effort
▪ It was a flat-out lie. ▪ a flat-out refusal
▪ a flat-out effort
