Fit refers to how tight the clearance is between a shaft and hole. Fits range from loose, free, medium, transitional to interference fit. In metric the system ranges from E6 being very loose to R7 tight interference fit.
Loose weight. That would be "lose weight" not "loose" weight. Lose is to not be able to find something you are looking for or to shed weight. Loose is when something is not secure or does not fit tightly.