This is the 10064th most frequent Polish word.
bezmyślną
"Bezmyślną" means "thoughtless" in English.
In this sentence, 'bezmyślna' is used to describe the decision as lacking thought or care.
To była bezmyślna decyzja z jego strony.
That was a thoughtless decision on his part.
Here, 'bezmyślną' describes the manner in which the task was carried out as lacking thought or consideration.
Wykonał zadanie w sposób bezmyślną, nie zastanawiając się nad konsekwencjami.
He performed the task thoughtlessly, without considering the consequences.
In this case, 'bezmyślną' characterizes the action as irresponsible or careless.