The human brain (sense 1a) considered as the centre of mental activity; the organ of thought, memory, or imagination. Also in plural.

Chiefly humorous. The skull; the brain; the mind. Now rare.

Originally: (more fully common sensorium, †first sensorium) a (supposed) seat or centre within the brain in which sensations are united (cf. common…

The skull as the centre of thought, memory, or imagination, the mind. Cf. brain, n. 3a, head, n.1 2a, noddle, n.1 1c, skull, n.1 1b.

= pericranium, n. 2.

The skull; the brain, the mind; = pericranium, n. 2.

The brain, esp. as the seat of a person's intelligence or intellect.

The brain or mind, as the place where memories are stored; a person's memory or store of memories. Frequently colloquial and humorous.

U.S. colloquial. The brain as the organ of thought; (hence also, by extension) the head. Cf. think box n. at think, v.2 compounds. Now rare.

the brain as the organ of thought.

(a) = think box n. at think, v.2 compounds; (b) a room used as a study (rare).