adjective

not giving sufficient attention or thought to avoiding harm or errors.

she had been careless and had left the window unlocked

inattentive,incautious,negligent,remiss,forgetful,absent-minded,heedless,irresponsible,impetuous,reckless,sloppy,couldn’t care less,slap-happy,shoddy,slapdash,slipshod,scrappy,slovenly,unconsidered,amateurish,lax,slack,wild,disorganized,hasty,hurried,perfunctory,cursory,thrown together,sketchy,hit-or-miss,inaccurate,imprecise,inexact,incorrect,wrong,erroneous,error-ridden,scatterbrained,thoughtless,unthinking,insensitive,indiscreet,unguarded,ill-advised,ill-considered,ill-thought-out,unwise,misguided,inadvertent,rash,foolhardy,spur-of-the-moment,hare-brained,negligent in,mindless of,heedless of,improvident about,unconcerned about,indifferent to,oblivious to,reckless about,remiss in,slapdash about,slipshod about,frivolous about,sloppy in,messy in,half-arsed,half-assed