an unkempt or uneven tangled mass or covering, e.g. of hair
long coarse or matted fibre or nap
a shag pile carpet
a strong coarse tobacco cut into fine shreds
a European bird related and similar to but smaller than the cormorant: Phalacrocorax aristotelis
[Old English sceacga rough or matted hair; (sense 3) perhaps from the bird's shaggy crest]