What does "Gross" mean in this pic?

I'm not sure what the cartoonist means by "gross" in the top picture.

In the 2d drawing 'science-y' just means 'like a scientist.' In other words, one purpose of wearing the lab coat could be to feel like a professional in the lab.

Thanks.
But what does y stand for here?

Gross means disgusting. The more effort you putting into eating good food, the more the gross factor goes down, or the grosser the food the less effort you have to put into to get it.
So on this scale, vending machine food is the worst and if you want to eat really well, you actually have to get off your duff and go to a decent restaurant off campus.
The -y is there for effect. If he wrote sciencey it would look like a spelling mistake. The cartoonist is deliberately emphasizing the mistake to say science-y, pronounced sciencee. It's like truthiness or other made up words, especially in advertising, that describe an idea.
In this diagram or joke, it's saying a large group of people who wear lab coats are wearing a costume in a way, using the coat to appear to be scientists, or smart or scientist like.
Once you describe a joke, it loses it's funny.

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http://www.collinsdictionary.com/dictionary/english/-y
-y1 or -ey

Definitions
suffix forming adjectives

from nouns characterized by; consisting of; filled with; relating to; resembling ⇒ sunny, sandy, smoky, classy

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You're just being Contrex-ey/McTag -y/Ceili-ey/jtt-y/

Good stuff.

Of course, you know the many, many "standard" words that have become so mainstream that they don't use the hyphen y [-y/-ey] that situation coined words do, Ori.

These have endings that include: acy, cy, sy, ty, ery, ry, ancy, ency