Alaska crab vs crab

Alaska crab and crab both are nouns.

Word	Noun	Adjective	Verb	Adverb
Alaska crab	Yes	No	No	No
crab	Yes	No	Yes	No

As nouns, crab is a hypernym of Alaska crab; that is, crab is a word with a broader meaning than Alaska crab:

Alaska crab: large edible crab of northern Pacific waters especially along the coasts of Alaska and Japan
crab: decapod having eyes on short stalks and a broad flattened carapace with a small abdomen folded under the thorax and pincers

As nouns, crab is a hypernym of Alaska crab; that is, crab is a word with a broader meaning than Alaska crab:

Other hypernyms of Alaska crab include crabmeat.

Alaska crab (noun)	crab (noun)
large edible crab of northern Pacific waters especially along the coasts of Alaska and Japan	a stroke of the oar that either misses the water or digs too deeply
meat of large cold-water crab; mainly leg meat	decapod having eyes on short stalks and a broad flattened carapace with a small abdomen folded under the thorax and pincers
	a louse that infests the pubic region of the human body
	the edible flesh of any of various crabs
	a quarrelsome grouch

Alaska crab (verb)	crab (verb)
	complain
	fish for crab
	scurry sideways like a crab
	direct (an aircraft) into a crosswind