やけくそ (yakekuso) means “a state of mind where one loses one’s rational thoughts and takes a f*ck-it, YOLO, I-don’t-give-a-sh*t-anymore attitude”. Typically, people reach this state when they have a complete failure and end up facing a tough and stressful situation, e.g. losing piles of money on gambling, or being rejected by their crush in a pitiless way. A common behaviour of people who get yakekuso includes eating/drinking excessively, giving up everything, and spending loads of money without a second thought to the consequences.
Other than in hiragana, it is also written in katakana ヤケクソ or kanji 自棄糞, although the kanji form is not commonly used. In fact, やけくそ is a coarse way of saying やけ, with くそ coming from 糞 (“sh*t”) as shown in the kanji form.
カジノで3万円負けて、やけくそ (or やけ) になって後5万円賭けたら全部擦った
Having lost 30k yen at a casino, I got yakekuso and bet 50k more, losing all of them
* 擦(す)る means “lose money on gambling”
I tried to cook carbonara but it didn’t taste good, so I got yakekuso and put a huge amount of mayonnaise into it.