'Skull' definitions:

Definition of 'skull'

noun

The bony skeleton of the head of vertebrates

From: GCIDE

Skull \Skull\, n. [See School a multitude.] A school, company, or shoal. [Obs.] [1913 Webster]
A knavish skull of boys and girls did pelt at him. --Warner. [1913 Webster]
These fishes enter in great flotes and skulls. --Holland. [1913 Webster]

From: GCIDE

Skull \Skull\, n. [OE. skulle, sculle, scolle; akin to Scot. skull, skoll, a bowl, Sw. skalle skull, skal a shell, and E. scale; cf. G. hirnschale, Dan. hierneskal. Cf. Scale of a balance.]
1. (Anat.) The skeleton of the head of a vertebrate animal, including the brain case, or cranium, and the bones and cartilages of the face and mouth. See Illusts. of Carnivora, of Facial angles under Facial, and of Skeleton, in Appendix. [1913 Webster]
Note: In many fishes the skull is almost wholly cartilaginous but in the higher vertebrates it is more or less completely ossified, several bones are developed in the face, and the cranium is made up, wholly or partially, of bony plates arranged in three segments, the frontal, parietal, and occipital, and usually closely united in the adult. [1913 Webster]
2. The head or brain; the seat of intelligence; mind. [1913 Webster]
Skulls that can not teach, and will not learn. --Cowper. [1913 Webster]
3. A covering for the head; a skullcap. [Obs. & R.] [1913 Webster]
Let me put on my skull first. --Beau. & Fl. [1913 Webster]
4. A sort of oar. See Scull. [1913 Webster]
Skull and crossbones, a symbol of death. See Crossbones. [1913 Webster]