From WordNet (r) 3.0 (2006) [wn]:
wacky
adj 1: ludicrous, foolish; "gave me a cockamamie reason for not
going"; "wore a goofy hat"; "a silly idea"; "some wacky
plan for selling more books" [syn: cockamamie,
cockamamy, goofy, sappy, silly, wacky,
whacky, zany]
2: informal or slang terms for mentally irregular; "it used to
drive my husband balmy" [syn: balmy, barmy, bats,
batty, bonkers, buggy, cracked, crackers, daft,
dotty, fruity, haywire, kooky, kookie, loco,
loony, loopy, nuts, nutty, round the bend, {around
the bend}, wacky, whacky]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Wacke \Wack"e\, Wacky \Wack"y\, n. [G. wacke, MHG. wacke a large
stone, OHG. waggo a pebble.] (Geol.)
A soft, earthy, dark-colored rock or clay derived from the
alteration of basalt.
[1913 Webster]