Extrinsic muscles. Definition. noun. A group of muscles lying superficially on a structure, in contrast to intrinsic muscles, which are located deeply. Supplement.For instance, the extrinsic muscles of the tongue include genioglossus muscle, hyoglossus muscle, styloglossus muscle, and palatoglossus muscle.Since they are extrinsic muscles, they are located on the surface of the tongue, and attach the tongue to other structures.xtrinsic muscles. Definition. noun. A group of muscles lying superficially on a structure, in contrast to intrinsic muscles, which are located deeply. Supplement.