noun: An inflated ego, an exaggerated belief in one's own importance.
noun: (idiomatic, usually humorous) The brain, as opposed to the penis, little head; rational thought, as opposed to lust.
noun: (Jamaica, slang) to be under the effect of cannabis.
noun: Alternative spelling of bighead [(countable, colloquial, especially used by children) A person having an inflated opinion of himself; a conceited or arrogant person.]