The quality of being brainless; stupidity, foolishness, or lack of intelligence.
Noun formed from 'brainless' by adding -ness. 'Brainless' combines 'brain' + -less (without), so brainlessness is the abstract quality of lacking brain or intelligence.
This word sits at an interesting intersection—it's both harsh (insulting someone's intelligence) and somewhat philosophical (acknowledging that some actions reveal an absence of thought). Medieval philosophy used similar logic with 'mindlessness.'
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