(noun)
broadly, a covering or mass of long, coarse/rough, and tangled material, especially hair or fur;
e.g. The puppy looked like a shag of fur and couldn't see where it was going.
(noun)
a haircut in which the hair is relatively long and cut into uneven layers;
e.g. He wore his hair in a shag that kept falling into his eyes.
(noun)
any of the waterbirds characterized by dark greenish-black feathers and a hooked bill;
e.g. They sighted a shag when birdwatching by the lake.
(noun)
an American dance style that was popular in the 1930s and 1940s, characterized by lively footwork such as hopping on one foot and then the other, often without moving the upper body much;
e.g. They danced the shag and had great fun at the party.