名詞 cracker:

1. a thin crisp wafer made of flour and water with or without leavening and shortening; unsweetened or semisweet
   同義詞：cracker
2. a poor white person in the southern United States
   同義詞：redneck, cracker
3. a programmer who `cracks' (gains unauthorized access to) computers, typically to do malicious things
   同義詞：cracker
4. firework consisting of a small explosive charge and fuse in a heavy paper casing
   同義詞：firecracker, cracker, banger
5. a party favor consisting of a paper roll (usually containing candy or a small favor) that pops when pulled at both ends
   同義詞：cracker, snapper, cracker bonbon

形容詞 crackers:

1. informal or slang terms for mentally irregular
   同義詞：balmy, barmy, bats, batty, bonkers, buggy, cracked, daft, dotty, fruity, haywire, kooky, kookie, loco, loony, loopy, nuts, nutty, round the bend, around the bend, wacky, whacky

1. Some of my friends like soda crackers.
   我的一些朋友喜歡蘇打餅干。
2. The boys light crackers in the street.
   男孩們在街道上放鞭炮。

crack.ers

adj.Chiefly British （形容詞）【多用于英國】
Insane; mad.
瘋狂的；發(fā)瘋的

來源：
Probably from cracker [breakdown]
可能源自 cracker[崩潰]