1. 不谨慎的;粗心大意的;轻率的
If you say that someone is incautious, you are criticizing them because they do or say something without thinking or planning.
1. carelessly failing to exercise proper caution
e.g. an incautious step sent her headlong down the stairs
2. lacking in caution
e.g. an incautious remark
incautious talk