Definition
Someone who is cute or attractive.
Origin Of The Word
The earliest known use of the phrase "snack" to mean attractive appeared on Twitter on July 6th, 2009 by Twitter user @BeautyMark_Tee.
Examples
How It Spread
The phrase saw use online over the next several years, mostly on Twitter, in captions to selfies or comments on others’ pictures. For example, On December 11th, 2015, Twitter user @xocatilinia_ posted a selfie with the caption "lookin like a snack" which gained a retweet and eleven likes (shown below).
The phrase began seeing more widespread use in meme contexts in the beginning of 2017. It would not be used in its original context but instead with joke variations on Twitter. A popular example of the phrase is a tweet by @ConnorKennedyy that used a picture of Squidward posted November 2nd, 2017 (shown below)