1.  devil-may-care(s = adj.all) carefree, freewheeling, happy-go-lucky, harum-scarum, slaphappy - cheerfully irresponsible; "carefree with his money"; "freewheeling urban youths"; "had a harum-scarum youth"

2.  devil-may-care(s = adj.all) raffish, rakish - marked by a carefree unconventionality or disreputableness; "a cocktail party given by some...raffish bachelors"

N  rashness, temerity, want of caution, imprudence, indiscretion, overconfidence, presumption, audacity, precipitancy, precipitation, impetuosity, levity, foolhardihood, foolhardiness, heedlessness, thoughtlessness, carelessness, desperation, Quixotism, knight-errantry, fire eating, gaming, gambling, blind bargain, leap in the dark, leap of faith, fool's paradise, too many eggs in one basket, desperado, rashling, madcap, daredevil, Hotspur, fire eater, bully, bravo, Hector, scapegrace, enfant perdu, Don Quixote, knight-errant, Icarus, adventurer, gambler, gamester, dynamitard, boomer, rash, incautious, indiscreet, imprudent, improvident, temerarious, uncalculating, heedless, careless, without ballast, heels over head, head over heels, giddy, wanton, reckless, wild, madcap, desperate, devil-may-care, hot-blooded, hotheaded, hotbrained, headlong, headstrong, breakneck, foolhardy, harebrained, precipitate, impulsive, overconfident, overweening, venturesome, venturous, adventurous, Quixotic, fire eating, cavalier, janty, jaunty, free and easy, off one's guard, post haste, a corps perdu, hand over head, tete baissee, headforemost, happen what may, come what may, neck or nothing, the devil being in one, non semper temeritas est felix, paucis temeritas est bono multis malo.

N  insolence, haughtiness, arrogance, airs, overbearance, domineering, tyranny, impertinence, sauciness, flippancy, dicacity, petulance, procacity, bluster, swagger, swaggering, bounce, terrorism, assumption, presumption, beggar on horseback, usurpation, impudence, assurance, audacity, hardihood, front, face, brass, shamelessness, effrontery, hardened front, face of brass, assumption of infallibility, saucebox, insolent, haughty, arrogant, imperious, magisterial, dictatorial, arbitrary, high-handed, high and mighty, contumelious, supercilious, overbearing, intolerant, domineering, overweening, high-flown, flippant, pert, fresh, cavalier, saucy, forward, impertinent, malapert, precocious, assuming, would-be, bumptious, bluff, brazen, shameless, aweless, unblushlng, unabashed, brazen, boldfaced-, barefaced-, brazen-faced, dead to shame, lost to shame, impudent, audacious, presumptuous, free and easy, devil-may-care, rollicking, jaunty, janty, roistering, blustering, hectoring, swaggering, vaporing, thrasonic, fire eating, full of sound and fury, with a high hand, ex cathedra, one's bark being worse than his bite, beggars mounted run their horse to death, quid times? Caesarem vehis, wagahai wa (expressing superiority).