Definition of "brainless"
adjective
comparative more brainless, superlative most brainless
(not comparable) Having no brain.
Quotations
Surely it was more likely that a brainless creature, acting solely by vague predatory instinct, would give up the chase when I disappeared, and, after a pause of astonishment, would wander away in search of some other prey?
1912, Arthur Conan Doyle, The Lost World […], London, New York, N.Y.: Hodder and Stoughton
(comparable) Unintelligent, with little common sense.
Quotations
"I don't mean all of your friends—only a small proportion—which, however, connects your circle with that deadly, idle, brainless bunch—the insolent chatterers at the opera, the gorged dowagers, the worn-out, passionless men, the enervated matrons of the summer capital, […]!"
1907 August, Robert W[illiam] Chambers, chapter VI, in The Younger Set, New York, N.Y.: D. Appleton & Company