1) Adventuresome 2) Adventurous 3) Brainish 4) Careless 5) Heedless 6) Hotheaded 7) Impetuous 8) Impulsive 9) Lacking in caution 10) Madcap 11) Not cautious 12) Reckless 13) Tearaway 
• (a.) Not cautious; not circumspect; not attending to the circumstances on which safety and interest depend; heedless; careless; as, an incautious step; an incautious remark.
In·cau'tious adjective [ Prefix in- not + cautious : confer Latin incautus .] Not cautious; not circumspect; not attending to the circumstances on which safety and interest depend; heedless; careless; as, an incautious step; an incautious remark. « You . . . 
[adj] - lacking in caution 2. [adj] - without out proper caution 3. [adj] - displaying or feeling no wariness
incautious, incautiously Not cautious; wanting in caution; careless, heedless, unwary, rash.
adjective carelessly failing to exercise proper caution; `an incautious step sent her headlong down the stairs`
not cautious; careless; reckless; heedless.