[1] : WordNet (r) 2.0

slaphappy
     adj 1: cheerfully irresponsible; "carefree with his money";
            "freewheeling urban youths"; "had a harum-scarum
            youth" syn: carefree, devil-may-care, freewheeling,
             happy-go-lucky, harum-scarum
     2: dazed from or as if from repeated blows; "knocked silly by
        the impact"; "slaphappy with exhaustion" syn: punch-drunk,
         silly
     also: slaphappiest, slaphappier
see also:
carefree devil-may-care freewheeling happy-go-lucky harum-scarum punch-drunk 
silly slaphappiest slaphappier 

[2] : Moby Thesaurus II by Grady Ward, 1.0

50 moby thesaurus words for "slaphappy":
   balmy, bananas, barmy, bats, batty, beany, bedazzled, bonkers,
   buggy, bughouse, bugs, crackers, cuckoo, daffy, dazed, dazzled,
   dippy, dopey, dotty, flaky, flipped, freaked-out, fruitcakey,
   fruity, gaga, goofy, groggy, haywire, in a daze, just plain nuts,
   knocked silly, kooky, loony, loopy, mazed, nuts, nutty,
   off the hinges, off the track, off the wall, potty, punch-drunk,
   punchy, round the bend, screwball, screwballs, screwy, silly,
   wacky, woozy

Slaphappy >> S Words
Slaphappy, definition of term: Slaphappy
slaphappy_pag1.html