This is less a definition and more an example of the historical use of the word "unfuck" from my personal experience. True story. The example should be self explanatory but some background is in order. I was probably one of the youngest sergeants in the USMC with almost two years in grade on the 4th of July 1970. I was about halfway through my second tour in Vietnam. We just returned from an 8-day patrol and had some time off. About ten of us headed down to the beach where we celebrated the 4th by drinking, smoking, shooting off some 300 or so pop flares, a few thousand rounds of M-60 tracer rounds, I made some firecrackers from C4 and det chord. Still had one of those left when I noticed our fire out and wood supply depleted. Being the resourceful ranking Marine I used my leadership skills to point out the adjacent USO and its ample wood supply. There must have been forty to fifty picnic tables. Huge ones that were made out of some damn fine lumber and they made a damn fine bonfire. We did them all over the next few hours, four to five added as needed to spark things up. I felt like a real patriot.
Hungover, and as ranking member of the pinic table assualt team, I was called on the carpet next morning where my CO and First Shirt were giving me some 'feedback' on my leadership skills. When I laughed at them accusing me of signalling the enemy, for some reason they got really mad. First Shirt bumps up next to me and with his lips next to my ear he yells, "You best unfuck your attitude. You can fly with the nightowl if you want but you best be ready to scream with the Eagle in the morning."
True story and just one of many contexts in which the versatile "unfuck" adds value to your formal command of the English language.