The grest is the word 'great' and 'best' combined together to form the worst 'grest' It is an adjective used to describe something so breath taking and out of this world.
A state of being that occurs most typically in college students, or anyone with bad time management skills. The defining characteristic is a lack of time for shaving and/or bathing due to homework tasks to be completed during an all nighter, creating a grizzle on the face, and a proverbial crust.
Dude, I waited til last night to do that 15 page research essay. I was up all night and I'm hella Grusty right now.