Having three heads.

dull-witted

Foolish; dimwitted. / Having a mullet hairstyle.

(nautical) Built with the stern nearly straight up and down.

(colloquial) giddy; frivolous; foolish

(obsolete) Mentally dull; stupid.

(colloquial, dated) stupid

Having two heads; two-headed.

Having two heads or faces on one body. / Directed by two heads or chiefs; existing under two coordinate authorities.

Alternative form of pigheaded