SAD SACK /SADD SAKK/ noun: A commuter who places his/her knapsack, gym bag, French horn case and other personal effects on the empty seat next to them to dissuade potential seatmates from sitting there.
Usage: This Sad Sack on the 6:10 gave me a dirty look when he had to move all of his worldly possessions to the overhead rack to make room for me.
I like the sad sack, it made me laugh.
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