Couples who are constantly feeling the need to be touching, holding hands, kissing, and calling eachother pet names like shmoopy, as if they are forever caught in the state of being a brand new couple that is madly in love. It's from seinfeld
That is the shmoopiest couple I have ever seen. They are always eskimo kissing in front of everyone and it's awkward as hell.
Is something that you love so much or is a very cute animal, can be used to refer to pretty much anything. Once you start using it, you'll know.
When seeing a cute animal you might say "Oooo look at that shmookie. That's the cutest shmookies I have every seen!"
Or
When referring to a significant other "I love you shmookie, thanks for the best valentines day ever."
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CAN ALSO BE USED AS A VERB: "Give me a shmooks." means "Give me a kiss".