Example sentences:

Ramayana: Though Kumbhakarna rebuked Ravana for his reckless abduction of Sita, he stopped short of calling his brother feckless — the king’s face needed to be saved. 

Mahabharata: Duryodhana’s ill-advised attempt to humiliate the Pandavas, which had backfired badly with his being arrested by the Gandharvas, exposed him to be a feckless fool. 

Bhagavad-gita: If we listen uncritically to our restless mind, it will make us feckless in both senses of the word: it won’t let us do anything responsibly and it won’t let us do anything effectively.