adj characterized by pertness or impudence; saucy; impudent; bold; forward
n An impudent, saucy person
From Old French apert, from Latin apertum, open and prefix mal, bad
By the face of God!” he said, “Waldemar Fitzurse, much hast thou taken upon thee! and over malapert thou wert to cause trumpet to blow, or banner to be raised, in a town where ourselves were in presence, without our express command.” ~Ivanhoe
For the trivia buffs, Malapert happens, also, to be the name of a lunar crater.