不小心的意思是无意间或者缺乏注意造成的事故或错误。，不小心打翻杯子、忘记关灯等都属于不小心的行为。

How to pronounce: /bù xiǎo xīn/

Usage:

不小心 is usually used as an adverb, modifying verbs to indicate an unintentional or careless action.

Example sentences:

1. 我不小心把水杯打翻了，桌子上都是水了。(I accidentally knocked over the water cup, the table is all wet now.)

2. 昨天晚上我不小心把门关得太猛，吓到了邻居的猫。(Last night I accidentally closed the door too hard and scared my neighbor's cat.)

3. 他一不小心就把手机掉进了马桶里，真是倒霉。(He accidentally dropped his phone into the toilet, what a bad luck.)

4. 小孩子们玩得太起劲，不小心把花盆给打碎了。(The children were playing too rough and accidentally broke the flower pot.)

5. 我一不小心就迟到了，老板很生气。(I accidentally overslept and was late, my boss was very angry.)

Synonyms and usage:

1. 疏忽 (shū hu) - to neglect or overlook something due to carelessness or lack of attention.

Example: 他因为疏忽而错过了重要的。(He missed an important meeting due to carelessness.)

2. 失误 (shī wù) - a mistake or error made unintentionally.

Example: 他的失误导致了整个团队的失败。(His mistake led to the failure of the whole team.)

3. 粗心 (cū xīn) - careless or thoughtless.

Example: 我们要小心谨慎，不要因为粗心而犯错。(We need to be careful and not make mistakes due to carelessness.)

Editor's summary:

不小心 is a commonly used adverb to describe an unintentional or careless action. It can be used in various situations and is often followed by a verb. Other synonyms such as 疏忽, 失误, and 粗心 can also be used to express a similar meaning. Be careful and pay attention to avoid making mistakes due to being 不小心.