Lacking intelligence or thought; senseless. The movie was a mindless action flick with no real plot.
Done without thought or consideration; automatic. He gave a mindless nod, not really listening to what was being said.
Not requiring mental effort; simple or repetitive. Folding laundry is a mindless task that allows me to relax.
Disregarding or showing no concern for something; oblivious (usually followed by 'of'). He strode forward, mindless of the rain soaking his clothes.