Blub is a nickname to call a loved one such as a girlfriend/boyfriend. It can also be used to address a person/animal that is related to you, cute, chubby, or lethargic.

There are only two true blubs in the world though.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

Someone really cute and chubby

The slang term for blubber, used because it sounds better, and is more pleasing to say

The sound a fish makes.

A blub is the German pet name for a water bong, due to the noise it makes as the chronic passes through the water. Also known as a Blubber or a Blubbi.

The blackest and one of the most versatile words in the human vocabulary, Blub is a term used to define anything which is untasteful. It can be used to describe a state of being or a single thought or emotion. However, it is not a word that can be accurately put to use as an insult, for example, Calling someone "A blub" or anything else defining blub as a singular object is completely innacurate, as blub truly is in and of itself.
It is a word that should only be used in the most vile and dire of circumstances.