Incautious
/ɪnˈkɔːʃəs/
Definition 1 of 1
Pro Tip 1/3Impulsivity Warning
The term implies acting without thinking through potential consequences, usually leading to negative outcomes. 
Her incautious decision to skip exam preparations resulted in a failing grade.
Pro Tip 2/3Negative Implication
'Incautious' often carries a negative connotation, suggesting negligence or irresponsibility. 
His incautious driving endangered everyone on the road.
Pro Tip 3/3Social Context
Using 'incautious' when discussing someone's actions can imply a careless disregard for social norms or etiquette. 
Making incautious jokes in a formal meeting can be seen as offensive.