Synonyms of slap-happy in English:

slap-happy


See definition of slap-happy

adverb

1‘Drysdale's slap-happy friend’

SYNONYMS
happy-go-lucky, devil-may-care, carefree, cheerful, breezy, easy-going, nonchalant, insouciant, blithe, airy, casual, irresponsible
ANTONYMS

serious, solemn

2‘the slap-happy way the tests were carried out’

SYNONYMS
slapdash, careless, slipshod, lackadaisical, hasty, hurried, disorganized, haphazard, unsystematic, untidy, messy, thrown together, last-minute, hit-or-miss, offhand, thoughtless, heedless, negligent, neglectful, remiss, cursory, perfunctory, lax, slack
sloppy, shambolic, all over the place
British all over the shop
ANTONYMS

careful, meticulous, painstaking

3‘she's a bit slap-happy after such a narrow escape’

SYNONYMS
dazed, stupefied, punch-drunk, unsteady, wobbly